Should I stay or go?

Go. Honesty is the number one thing. My boyfriend had a few dark stories to share and while they weren't pretty he told me early on and we are still together years later. The one thing I can count on is his honesty when I ask him a question. He even told me when he kissed a girl a week before we moved in together. It really hurt, but I appreciated he told me as soon as it happened and didn't lie despite all his friends trying to cover for him.

All I can think is if he hid that serious of stuff on you what else is there?!

I have a guy friend that lies about that stuff and trust me his girlfriend things she's uncovered it all but she hasn't scratched the surface and we've told her that he is not truthful but she keeps giving him chances because he's in therapy and "turning his life around" but we see him lying still all the time. He will only truly change when he knows what loss is. He knows he can get her back with a few months of counseling, laying off the partying, etc.

That's tough. I feel the same way about lying. 

It sounds like he has been there for you through a lot. maybe his addictions, his vices, are what helped him when he was trying to be strong for you. 

He seems like he is willing to get help now that everything is out in the open. Based on what you have said, I would give him a fighting chance. If things don't change and either more lies come to the surface or more are made- it might be time to cut your losses. Good luck! 

So he had problems he hid from you (perhaps to protect you while you were in a delicate state of mind) so he could get you through your own issues. In, effect putting you first. You do say he has always been "kind, appreciative, attentive, supportive, loving and just the greatest partner I’ve ever known. " but now you are on your feet you want to abandon him?

I'd say since he stuck by you, has "taken full responsibility of these issues and has already made a counseling appointment for tomorrow." you need to be just as willing to be there for him as he was for you.

At least til you see if his effort to beat the addictions matches his promise to deal with them.

Geez Louise- he's staying with you despite your mental illness, but you're not willing to help him with his? Porn and gambling addictions are mental illnesses- people have genes for addiction, which can take several forms. IF he's willing to seek help for his addictions, cut the guy some slack. You're not perfect, either. 

He owned up to his issues and has a counseling appt tomorrow. Give him a chance to change but don't allow him to just go to a counselor one time. He may need to invest in counseling combined with couples counseling in addition for several months before he can be trusted.