I had 4 sinus infections in a month 1/2 I waa told it was because I had allergies that I didn't know I had. Can allergies cause sinus infections?

In a way. Allergies cause sinus and nasal mucus production, as well as swelling of the lining of the nose and sinuses. Since the openings into the sinuses are pretty small to begin with, swelling+drainage+any bacteria that got into a sinus=sinus infection. Work with your doctor to get your allergies under control, and your rate of sinus infections should drop. Feel better!
Can do. See ENT too. Allergies can get passages inflamed, can't drain as well, get infected. Can also lead to nasal (inflammatory) polyps which increase risk for infections too. Get a good ENT evaluation to rule out anatomical predisposing porblems. Allergist can be good idea too.
It can be a factor. 4 sinus infections in 6 weeks may actually be one infection that was difficult to clear up. Allergies can be an underlying factor, but not the actual cause. Having a consult with an allergist sounds like a good idea to help you figure out what is going on.