"Hard though it is, the best way to get over someone, also gives the highest chance that the other person will miss you enough to think about coming back and regret their decision, that is to stay no contact. Waiting to see, will he contact or won't he though, is the part that is going to set you back with getting over him, and bring you down more on your birthday. So take charge and block his number, don't let him ruin your Birthday, don't fill your head with wondering what he will do for the next 2 weeks."
This.
Hard as it is, it sounds like the relationship has run its course for him. Even if he is making silly excuses for why he feels this way, he is at least not trying to blame it on you. Ignore what he's saying: look at what he's doing - if he wanted to be with you, he would be with you. He's choosing not to be. Instead he's choosing to pursue another woman. He's not doing that because he misses you and regrets what he's done. He's pursuing another woman because, now he has ended the relationship with you, he can pursue other women. If he was still with you, it would be cheating. But he's not with you and it isn't.
It's going to hurt like hell for a while but most of us have been there and we can guarantee that the pain will pass. It will take time and generally the only way out of it is through it. But it will pass and you will learn a very important lesson which is that you can have your heart broken and still, in time, find pleasure, enjoyment and fulfillment in life and also, in due course, love. I say that because a terrific acquaintance of mine - in her late 30s - recently told me that she had never allowed herself to fall in love because she was so scared of getting hurt. And she's becoming increasingly aware of all the wonderful and fulfilling opportunities and sheer relationship practice she has missed out on as a result.
You need to get busy and distracted with other things especially now lockdown has eased somewhat in most places so most of us are now able to go out and about and see friends etc, even if we have to meet outside, remain several feet apart and so on. You may find it difficult to concentrate but the more activities you fill your time with, the more distracted you will be. And you will start to notice that a few hours have gone by and you haven't thought of him and those periods of time - when you're not thinking about him - will increase as time goes by.
In particular, make some arrangements for your birthday which don't involve even talking to him on that day. I agree with PP that you should block him - that way you won't even be subconsciously waiting for him to get in touch because you will know he can't.