Problem while Penetrating Vagina. Help!

We both are virgin and tried sex for the first time with each other. I am not able to penetrate into her vagina; every time I try to go into her in missionary position, she resists due to pain (couple of other positions also didn't work). She would squeeze her legs or force them against my chest and consequentially, I am never able to penetrate her vagina fully. Even when I try to insert two fingers inside her vagina, she cries in pain. She says that after repeated attempts, even the entrance of vagina starts paining. Eventually, I loose erection I don't know why; maybe because of the depression due to failed attempts or due to my addiction to the porn (not sure). As far as lubrication is concerned, she gets wet without any problem. We just use saliva as additional lubricant, since we do not favor synthetic lubricants. We use dotted condoms and always indulge in sufficient foreplay. We also don't have any sort of stress which might trouble our sex life. Please help!