just relax. its ok. this happens to many newly married couples. you need to be less apprehensive at the time of sexual intercourse. you must try and induge in more foreplay, that will lubricate your vagine well so as to facilitate penetration. you can also try to use some lubricant jelly like xylocaine
jelly or ky jelly. you can tell your husband to gently dilate your vagina with his fingers first.this way the vagina will open up and help in complete penetration.after complete penetration you must keep lying down in the same position and keep a pillow beneath your buttocks to elevate your bottom( for better sperm deposition).