I feel pain when having sex. It's like my low stomach like he's sitting my cervix. Only when he's on top. Is this normal?

It is not normal. To have pain with intercourse. If you only have it in this position, you are probably right. Try avoiding that position.
Maybe, maybe not! If this has not happened before with him, in that position, it is not normal. You may have an inflammation of the cervix. See a doc and get checked. Some positions can be uncomfortable if the cervix is being bumped head on, so shift position a little, if this is not new.