Why is my girlfriend still uncomfortable when having ?

we are both 18 and in a loving relationship for 3 months and have been ualy active for 2. we use protection and always do a lot of forplay but when we begin to start it always seems hard to put it in and when it is she finds it very very painfull after the first few times it began to sting and bleed which i asumed was the hymen breaking but it is always still painfull and i get very worid and do everything possible to make it comfortable for her while we do it but it does not help and i am a little worid now she says it is not as painfull but just feels strange neither good or bad just an odd feeling is thier somthing wrong or that might help because i am trying anything i can to help her but does not seem to work. she is always comfortable as she normally asks to start it and am always gentle with her please can you give some advice preferably if you are a girl who will know this not some stupid guy who doesnt understand