After given birth to my baby I can feel my womb on d lip of my virginal and since then I have not been able to conceive. Its four years now please help me?

Prolapse. It sounds like you're describing a prolapse of either your womb (uterus) or bladder (cystocele) or both. This is a mechanical or anatomic issue and is repaired surgically. Go see your family doc or OB for your physical exam w/special attention to your complaint. Pre-conception counseling, too. Then discuss your surgical options w/your ob, especially if you want to get pregnant again. Good luck!
Dropping womb. You do need an exam to see what is wrong but it is likely a relaxation of the supportive ligaments of the uterus. You probably feel the cervix in the opening. If you are having normal intercourse then you probably have another cause for infertility. You need testing for the usual suspects that cause infertility. Best wishes.