I've name changed for this.
You have my sympathies, it's a really hard place to be. I know, because I have been there and fallen very much in love with another man.
Unlike you, I was always having crush after crush on other men throughout my marriage. What I couldn't admit out loud was just how unhappy I was. It is only with distance that I can see very clearly why and it was because ex and I were firstly very incompatible and secondly because he was very controlling and would put me down all the time.
Only you know in your heart of hearts if your marriage is worth saving. I don't know if you are in a full blown affair, or if the other man is in love with you too. Whatever, there is something wrong or missing with your current relationship.
Your decision after that soul searching is whether to work on your marriage or leave. What you don't do is have an affair for months and months - this isn't a trashy novel.
If you decide to leave, your children will be hurt and there will be times that it will rip your heart out. That is only fair, because it is what you have done to them. You will need to put everything into putting them first and helping them to navigate your decision.
Counselling is a good idea, you may be able to access telephone counselling through work. Even if you can only get to one session by saying you have a drs appointment, go. It will help you to clarify things in your head.
If you think you were raped by your current DH then please do access support. Other posters will help you with this.
You are going to need all your emotional strength to get through this. But you will, either way. Keep focusing on your DC.
You will get some negative replies here. Be strong.
For me, this happened more than 3 years ago. I left for the OM. We are still together and I love him with all my heart. I now see my ex for who he really is. For me, I made the right choice.
You need to work out the right choice for you. Good luck x