I'm having trouble getting my penis into my girlfriend's vagina. There are some things that would probably be better put in point form, so here goes:

-I am average sized, leaning towards the shorter side of the spectrum
-I'm sure that we were ready - she was dripping wet down there
-I "think" she's really tight. For reference, one finger would get squeezed pretty tightly; two fingers would require a good deal of force to get in
-We've tried missionary, doggie, standing up from behind, and standing up face to face
-It's worked out twice in the missionary position but was really hard to accomplish; we don't seem to be able to get it to work again
-We 'do it' with the lights on

My question is, am I doing something wrong? She even tries to cram my penis inside using her hands but for some reason, it does not work - I just don't feel like there is an opening... We've tried several times and it is pretty frustrating...

-Ps. For the two times it went in, it did not feel as great as I was led to believe it would. I think I have more fun with a handjob - is this normal?