Can't get over what I witnessed but we have a daughter.Should I or should I not get a divorce?

Me(43 years old) and my wife(42) have been married for 17 years.We have a daughter(12).In the beginning our marriage was going great.Eventually,though,me and her became distant.I really don't know why.Maybe it's because I'm always working,I'm not a workaholic but since she's a stay at home mom/housewife I have to work in order to support our family.She only makes sure the house is clean,does the dishes and helps our daughter with her homework.We stopped having sex that often.In fact we kind of stopped being attractive and sexy for one another.That special spark was gone.We were in a rut.However,I still managed to make time for her and she never complained.I have to admit though,our marriage felt like a responsibility,at least to me.Taaking care of our daughter,just having a lot on our plate.We were both busy,me as a businessman and her as a mom,of course,that's not an easy job-to take care of a child and maintain cleanliness at the house.It entails doing many chores.Nevertheless I think that's all normal.I think all families go through such periods.And like I said she's never complained about our sex life or anything.After witnessing what I'm about to narrate,I think she might've felt a bit lonely but let's cut to chase.Recently,she's been acting suspicious.I've been suspecting her of having a secret lover.

It was eating me up so I decided to talk to her about it.She laughed and said:Honey,don't be silly.I only have eyes for you and kissed me.I believed her but I also came up with an idea.I go out of town on business trips quite frequently.2 days ago,I decided to put her theory to the test so I lied I'd be going on a business trip for the weekend.What I did was I got home early and decided to surprise her with a romantic dinner like good old times.As I was picking up candles and other stuff from this box in the living room I heard the door open.It was her but she wasn't alone.She was laughing and apparently she was making out with another man.I thought i'd stay in the living room and see how far they go.They went straight to the kitchen.Thankfully they were so caught up in their act that they didn't close the kitchen door,they left it ajar.I steadily hid behind that door and observed as they were completely unaware they weren't alone.At first I couldn't see much but eventually they moved next to the dining table which happens to be opposite the door I was hiding behind.I caught my wife on her knees blowing some young guy very pationately as he was leaning against the dining table.He was already fully naked and she was only wearing one of my shirts,unbuttoned with an untied tie around her neck.I was so shocked.

She was making comments about how big and yummy his penis was and how she could suck it all day and he was asking her questions such as:"Bigger than your husband's?" and "Do you suck your husband with that much enthusiasm?" To which she replied:"I never do this for my husband,baby!" as she blew him for another 20 mins and then he came in her mouth and a little bit on her hair,it was a lot,some dripped on her boobs and on my shirt,there was also some on the floor.At that moment I was so shocked,so stunned,I wanted to interrupt them so badly but at the same time i couldn't believe that was my life.I wasn't even angry,I was just so humiliated,I felt worthless.I didn't even realize how fast time was going by as I was standing there watch that.After a couple of more mins of blowjobs,I had to watch that other man **** my wife on the table.And of course,later on, he came on her face.The guy went:"Oh man you're the best baby!"She laughed and said I quote:Shall I clean your cock like the obedient housewife that I am?" To which he didn't say anything so she looked into his eyes with a smirk on her face and put his dick back in her mouth for mere seconds,then put it back out,slid it across her lips and said I quote:"I'll give my husband a nice kiss when he gets home."and started giggling,then she added:"When he fucks me on Monday,I'll be thinking about you."and kept blowing him.I couldn't believe this was real life.Eventually they saw me,they noticed my presence.The guy quickly took his clothes and ran off.My wife started crying and apologizing.I was so angry that I left the house and went to this pub nearby.

It's a good thing our daughter was still at school.Who knows how far they would've gone if they hadn't seen me standing there.I didn't drink,I just stayed in the pub for hours.She wouldn't stop calling so I switched off my phone.Later on,when I switched on my phone I received a text message from her which read something along the lines of:You are the love of my life but I need to feel loved too.You weren't making me happy but now I've realized that I don't wanna lose you.I'm begging you to give me a second chance.If not for me,do it for our daughter.What should I do?File for divorce?And what about our daughter?My wife was so conservative.I never thought in my wildest dreams she was capable of this.And it's true what she said.She'ser given me head and we have never done anything kinky but that's because she'd never been kinky.That was just not the woman I married.It was as though I was on the set of a porno.I can't get over what I saw.I'm on the verge of a mental breakdown.That is just not her.And as hard as it may be to believe,despite what she did she's always been a great mother to our daughter so I don't know what to do.I'm at a crossroads.