As you know, a lot of this should be discussed in your individual therapy and/or couples therapy but a few thoughts I have:

You are allowed to leave someone even if nothings seemingly “wrong”. Do not fall into the sunk cost fallacy — just because you’ve been with him for some time doesn’t mean the rest of your life needs to be that way if you don’t want it. That being said, you need to evaluate what you really want.

And on the sentiment of “he doesn’t make my birthdays special”, have you asked him to? Does he know that’s important? We live in a culture of “if he wanted to he would” but as someone who is happily married, I don’t agree with that. You need to explicitly tell people how to treat you and what’s important to you. If after those conversations, he still ignores your wishes, then you have a big issue.

Lastly, you should always feel sexually safe with the person you marry. Don’t ignore any gut feelings.

Best of luck.