Please can you help me please.

Myself and my girlfriend have been datin for 6 months now and we have finally talked a bit bout sex and we have decided to try it.

We have attempted to have sex 5 times now and they always end up failures.

We do all the foreplay and i finger her and she does stuff to me but when it comes to the sex part we just cant seem to get the penis inside her.

We have tried it different ways and we have both thried guiding it in but it wont seem to go inbetween her lips.

We are gettin to the stage of givin up cause we dont know what is wrong.

Please can u help us she is gettin very upset bout all this and i feel its my fault.