I’m lost. Idk what to do...

So my boyfriend came clean to me that 2 weeks ago he cheated on me when I was gone on vacation. I have been with him for 3 years and he’s literally the love of my life. I do anything and everything for him and idk what to do. He’s begging me to stay apologizing, crying, telling me he won’t do it again. He told me he was desperate. But wtf. I have done nothing but love him, support him, and help him financially and this is what he does to me? When he left the other day to go get me some ginger ale because I was sick to my stomach over this I went through his phone and he had googled “ how to survive cheating”, and “couple therapy”. I didn’t bring it up to him because I told him I was leaving him. I told him I wasn’t going through this hurt again. So when he got back I didn’t ask him anything about what he googled and I made sure I refreshed his phone so he didn’t know I went through it. I just wanted to see if he would mention it to me. So last night he brought it up. Asked me if I’d go to therapy with him so we can work this. He said he needs to go to therapy to figure out why he does the things he does. So what do I do?! Do I leave, or do I try and work this out and go to therapy with him. Is there a chance that it could help and we could be okay? Or is it time I just walk away.