Is she cheating with my boss?

Hi all how is everyone doing?

I hope you can help me.

I have been with a girl and she might be cheating on me.
We used to work together and I think she might be chasing with my former employer. I curently don’t work there as my contract has been terminated after I have asked her and him if it is happening.

I do have a few proofs that suggest she used to have a sexual relationship with him before we started being together. They used to sneak out duringring lunch or after work for a quick sex. He is a married man with kids and I know his family well. His wife is a wonderful woman and I wanted to do right by her asking him about the adultery. Unfortunately I got sacked from work. Took them a few months to do it but eventually my contract has been terminated. Anyway this is the past I have a question about preset.

So my GF is doing a few things I find weird.
If you could read below and let me know what you think.
- obviously she still declines that she ever slept with him and am not hopping to get her to confirm it even thou I have proof of it
- she has all her notifications either turned off or just show which app has a new message
- in the past I have found nude and rude selfies like closeups of vaginal and ass whole area and also I seen those being sent to people on Spachat. That was before we meet. This is to give you an idea about the personality she has.
- she turns her location off, we use Find My Friends. She says her phone died but I know it hasn’t it is just in airplane mode or turned off. I do have a proof of it.
- she speaks of my former employer in a rude way and get very very angry when I mention him to the point where she makes me feel guilty and I keep apologising to her.
- she gets a lot of messages on her Instagram from guys
- this is the weirdest one for me. She keeps coming back from work with those weird stains on her underwear. I asked her what is it she always says it is just vaginal discharge as she is coming on her period but she can get this one day and the next day there is nothing. She does get them sometimes when we have sex and I know she wasn’t having sex with anyone else on that day but she also get them when we don’t have sex.
If you don’t mind ladies having a look at some photos of the underwear that would be appreciated. I know it is not a nice sight but would help me understand.

Edit [Moderator]: Link removed

Thank you so much for you help.
Please ask anything you want.