some cases was because of having too much sex...specifically, having wrong position, which the penis is not directly or properly inserted. like a clothes streching or is not properly wearing

could just be air trapped in the vagina...it happens..usually when it comes out its gonna make some sort of noise

The vagina is normally not an open tube but more like a fireman's hose without water. The walls are tightly against each other. In a cross section it will look like a capital H with the two vertical lines next to your legs and the horizontal line between them. It will only become a tube when you are sexually aroused.

The top of the vagina (at the cervix end) does form an open space and during sex this is called "tenting". For the entrance to "pop" it will thus have to be this air that escape. This is called "queefing" or "varting". Maybe the movement of the uterus and bladder are causing some of this air to be expelled. Do you typically get this after sex or exercise?

Some women will take on air by merely crouching or squatting and this the has to escape later. If the air escapes inwards towards the body cavity it is not healthy (dangerous). For this reason men should also not blow air into the vagina during oral sex.