Sex is natural. So long as it doesn't come in conflict with your personal belief about anything, like religious beliefs, social pacts, or especially your health you can have all of the sex you want.

No one here can prove whether sexual conduct is immoral or moral, it's based on an individual's values. There is no real good or bad, so all you can do is please yourself. If you're comfortable, do it. If you're not, don't.