Lots and lots of folks come here in your shoes. If you search for mono/poly you find much to read about and lots of advice that may help in your situation.
People do make relationships work well where one partner is mono and the other poly. It is possible.
Is that what you really want? There is nothing wrong with wanting a mono relationship. It works well for lots of people. Poly may not work for you and that is ok. Contrary to Disney and pop songs, love alone is not enough for a relationship to survive and thrive. There must be some basic compatibility too.