Devastatedandgrieving,
I am so very sorry for your grief and pain. I agree with hikingout in that SI may not be the right place for you, certainly not right now. I would look into grief counseling.
Regarding your loss:
* Deal with your grief first.
* Know that you will make it through this, and it will get better. (I know that doesn't help much right now, but when things get bad, keep it in mind.)
* Take care of yourself. You've experienced a great loss. It is supposed to hurt for now.
* Make sure you have a support system setup. It's okay to lean on others.
* Do not make any big decisions (financial, medical, situational) right now. If needed, ask people you trust to help you.
Regarding your infidelity:
I'm not sure everyone here would agree with me, however... I'm not sure if you really are cheating. Don't get me wrong, I assume from your comments that you are probably still legally married, and so being with someone else is legally infidelity. And it may have started out as an affair. However, you also mentioned that you moved out and are no longer with your spouse. If you made it clear to your husband that you no longer want to be with him, that you were leaving him, and he understood that also meant the possibility of you seeing someone else... then he had every opportunity to say, "No. Wait. Stay. I'll work on this." or "GTFO and divorce." Either way, you are not living together and not sleeping together, and physically and emotionally separated, and he is/was at least tacitly agreeing to the situation. This is just my opinion, of course, but I think leaving and moving out is a clear marriage separation. Legality aside, I feel that morally, you ended the marriage, and if so, then it's not infidelity. It's you getting on with your life without him in it.
I hope you find peace in all of this. My advice to you is go be someone you love. You no longer have to carry the guilt or burden of infidelity or secrecy. If you can get divorced, you might want to proceed. Start fresh. Learn to be you without a "him" for a while. Get some counseling if you can. Between the abusive husband, the illicit boyfriend, and the double life lived (I assume) for some time, you have a lot to unravel and deal with. You have the time now. So go deal with it. When you come out the other side of this, you will love yourself more and know joy again, no matter how impossible that may seem right now. If you do meet someone special again, you can enter the relationship more confidently, knowing that you have healthier boundaries and better relationship skills.
One last thing, two books I can recommend:
The book of forgiving - by Desmond Tutu
Rising Strong - Brene Brown