I also agree with a about the way people automatically think of drugs. This is simply a mental block. It's very common for men with new gf's. You want to please. You are anxious and well it has been some time too so your not used to it! The masturbation comment is also true and can cause issues in men who are single for long periods. Men will automatically make things much worst mentally. If it happens it plays on your mind and it will happen again and again.
The key is communication. Just let her know that you just find her so hot and you want to please her so your getting over excited. That you will be fine soon etc. Many women can't even reach orgasm through intercourse (unless stimulated during sex too). Sure you want to last long and have her in all the positions you fantasize about and not have to worry about anything.
But you can pleasure her in many ways. Direct clit stimulation is key. The key is to take time on her and just be concerned with her pleasure and you will be good to go. Once you get comfortable over time you will be fine. Nothing will be more confidence boosting that making her go crazy when your down on her (tongue, hands or both
).
Don't be down on yourself as that will translate to her. Cialis and viagra are good but may even make things worst as you have improved blood flow and well more turned on. You don't need drugs.
SSRI's were mentioned but you only use them if you have depression or anxiety... but yes they will make it harder to cum.
Take control and realize your fine and just have fun with her.