My partner

How awful for you.

Does he know that you have discovered what has been going on?

Have they been seeing each other?

You really need to tackle this head on. Stay calm but confront him. Don't let him lie to you; you are worth more .

Perhaps it could be a blessing in disguise; better to find out now. 

Life can be so cruel at the time but don't sell yourself short. After 30 years of marriage, I discovered my husband was having an affair. I fell for all of his lies/deceit. I am not saying this is happening to you but looking back I think that I would have done anything to keep him. Today, if I had the time over I would tell him where to go as on finding out  all it resulted in was 3  years of hell for me; i ended up with anxiety depression mainly due to the fact that he had controlled everything in our marriage. I gave up a good career for him and to raise a family .I basically had no money and no security. Everything we had planned for our future was all gone.

Be strong . I wish you luck. x