Urology

What you most likely need to do is to relax a lot more about the whole experience. It sounds like sex with your girlfriend (and in general) is pretty new for you, so not really surprising that your excitement level is so high that you ejaculate very quickly.

Some of what will happen with experience is that your excitement level will diminish and the urgency will subside, which will lead to longer lovemaking sessions. The measure of premature ejaculation is technically penetrative sex that lasts less than 2 minutes, however it is broadly defined as anytime earlier than you wanted ejaculation to occur.

There are lots of techniques to "training" your penis to become accustomed to the sensations of intercourse which will help you resist the over-stimulation that is leading to premature ejaculation.

Clearly your attention is divided and you're overstimulated if you have to ask if you have entered your partner. Go more slowly, watch yourself, and educate your brain on how to respond to the overstimulating situation. Don't rush. I understand it's in the heat of the moment, but as it becomes more natural and regular, the tendency will be for your body to treat the situation as "normal" and not to overreact to the stimulation.

It's frustrating, but hopefully you will (and your partner will) be patient with this new experience of intimacy, and it will settle down into something more natural feeling.

In the meantime, you may wish to change your masturbation habits so they simulate intercourse instead of whatever you're doing. If your penis is used to the feeling of a dry hand while sitting in a chair, change it to a lubricated hand while laying down (or however you approach your partner). That's just an example, but one of the ways your can "train" your penis to not overreact to a new situation.