Husband & his coworker

So earlier this year me and my husband were having issues and feeling disconnected. We got in a huge argument and he expressed to me how he felt I didn’t love him he felt I wasn’t treating him like a husband. I then expressed to him how I felt he should be more “present” in our marriage , go on dates, take initiative with things etc. I also asked him has he ever flirted with anyone at his job or has anyone ever flirted with him and he told me NO. we agreed we would change our ways and work on our marriage however nothing hadn’t changed. Well recently while he was at work his phone accidentally sends me a voice message and in the message I can hear him and a female coworker “playing” in a flirtatious way. I was so upset! I called him immediately and all he could say was I’m so sorry. When he got home I told him what is going on with him and that female at work and to be honest with me. He then tells me he started conversing with this woman 3 months ago he said he would walk over to her work area and start talking to her, she would tell him about her baby daddy and he said he had told her that he felt I treated him like I didn’t love him, he also stated that they told each other they liked each other he said he started to enjoy the fact that she was “nice” to him. He then tells me they have never spent time outside of work they never exchanged phone numbers they never hung out after work that he would just always talk to her during work hours sometimes. He also admitted that he did not tell the girl that he was MARRIED…I ended up talking to this woman myself and when I did she apologized and stated she had no idea he was married she also confirmed that everything my husband said was the truth , that they would only talk here and there at work and never hung out outside of work on lunch breaks or never exchanged phone numbers. This is the first time in the 5 years we’ve been together that I’ve ever caught him in a lie and anything involving another woman. My husband seemed remorseful , begging me not to leave him he stated he regrets what he’s done he said he was being selfish and he never wants to put me through this again he contacted the girl before I did and told her he’s married and that he should have never said anything to her , he stated he would do whatever it takes to gain my trust back, he stated he wants to be a better husband father and overall better man to me , he explained to me that he wants to go to couples counselor and all these good things he said that he’ll change his shift away from the girl, he says he will never let anyone come between us again. Ever since the incident he has been a totally different man doing all the things I’ve been wanting to do, he’s been giving me the best sick I’ve had from him in a while. He tells me he regrets what he did and seeing me hurt the way I was made him realize just how much I actually do love him he said this experience has taught him a lesson but I’m like how when it just happened a week ago??While all that is good , I feel like I’m still hurting from the break in trust, I just can’t trust him since this has happened, I feel like if his phone would’ve never sent me that message I would have never known, I feel betrayed , what if he’s only being good now because he got caught and not because he truly wants to get through this, what if he does this again and it’s worse? How do I know if he genuinely learned his lesson. Am I being dramatic? Was I too easy on him based on the circumstances? How can we work on building trust back is this something that’s fixable?