Desperate to save my marriage

I desperately need help to save my marriage. I have ADHD, I was diagnosed as a child and again about 6 years ago. I take Adderall  XR on a daily basis. I am ruining my marriage without meaning to. I'm lying to my husband, I've cheated on him,  I've destroyed any trust he had in me. We have been together for 15 years and married for over 13, he's my best friend, my everything.  I love this man with all my heart and don't know why I keep doing this destructive behavior. 

About a year ago I was drinking with some friends and ended up kissing another guy. I didn't mean to, I didn't plan to, it just happened.  My husband asked about that night and I lied to him. He recently found out I lied and now wants a divorce.

side note- 12 years ago I did have sex with someone else and have worked hard to make it up to him since.

i don't know why I keep doing this stuff. I'm happy with him, he's an awesome husband, and my everything. 

please give me advice on how to fix myself. I don't know where to start and it's really overwhelming. I started with a therapist last week and will meet at least once a week. What else can I do? See the Dr who prescribes my Adderall and change medications? Ever since insurance decided to only cover generics I haven't noticed it working as well, maybe I need to change meds? 

I'm desperate to save my marriage. This man means so much to me and I'm willing to do what ever it takes. I know I have a problem lying to him, I don't exactly know why I do it, I guess so he's not mad at me. I admit I need help, I just don't know where to start.

Thank you