Don't know what to do

Me and my husband has been together for 13 years and married 9 years and we been having problems for a real long time and here recently I ran in to an old friend and we started talking and and feelings started coming back and we been secretly been seeing each other for a while now and I'd left my husband a few months ago and he went crazy so I ended up coming back and I've regretted it ever since cause all I want is all the way out and go on with my life without all the hassle and threats I can't get this other guy off my mind he's all I think about and who I wanna be with and my only problem is that I'm scared of my husband and it would crush him if he ever found out and probly hurt somebody in the process I just know what I need to do im happy with one and miserable with the other