You should have negotiated this before you started employment.
Once, when I objected to terms that would have granted the company ownership over everything I did outside of work, they just swapped out that page with another one they had ready. The different terms were there and ready, but just not the default. They were perfectly happy to give me the rights to my own projects, as long as I was willing to ask for them.
It does suck when you didn't pay attention to what you signed, and are stuck in a bad situation, and it can be hard to fix these things after the fact.
Your best option would probably to look for another job, and pay attention to what they are asking you to sign.
Hopefully you don't have any long term non-competes, or other clauses.