Hey supraguy...

I wish there were really easy answers and solutions for these kind of problems. But usually it takes quite a lot of reading/counseling/changing to change these kind of things.

An idea is to learn more about Cognitive Behavioral Therapy. Perhaps buy a CBT workbook online somewhere.

When you're having a anxious/negative thought, become aware of it and catch yourself doing it. Then challenge yourself. Usually your thoughts come from year-long habits of thinking in ways. Sometimes these ways are not the best.

Btw, when you're girlfriend is out partying and you're alone, I think it's pretty normal to be a little worried about it. Of course if you trust your girlfriend completely it's no big deal. If you go with your girlfriend for a couple of times, I think the anxiety will go away.

One way to overcome anxiety is to slowly Expose yourself to anxiety-provoking situations. So every now and then, do some you feel anxious about. In the moment, watch your thoughts, and afterwards think if you can think differently and better about that situation.

You can definitely do something about anxiety. Good going that you're seeing a councillor, that can make a difference.