Can I catch a cold back from someone I gave it to?

I assume if its contagious then its viral and not an infection. Correct me if I’m wrong on this.

The crux of the question is, I had a summer cold which seems to be going around in this area of lurid heat and humidity. The endless months of Summer heat have always drained me, but this was debilitating even before I realized I was sick.

It was never all that severe and really didn’t even slow me down much more than the usual heat and oppression. But it lingered for over three weeks, and was most severe for maybe just two days. Even then, not all that bad.

My parents, who are very elderly and whom I help part of the day, never caught this. I was very careful. But my girlfriend, whom I share an apartment with, did. We were closer physically but still careful.

She had to have caught it from me because she is much more isolated. But she seems to have a much more severe case.

Am I likely to catch it again from her?

When I was in my early teens, my sister and I lived in the same house but almost never physically in contact (we shared the same bathroom but that’s about it), but kept giving each other strep throat over and over. So viruses can be obtained multiple times. Then again, I’ve heard that once you’ve caught a cold, you’re immune to that particular virus.

So which is it? Am I likely to get sick again from this?