I totally follow you. I did the same thing thing! I was analyzing words and text messages and all sorts. This isn't strictly an OCD thing, but if she makes you happy and you enjoy spending time with her, then above all else stay with her. It's your relationship and your opinion of her that matters, not your parents. That kind of negativity doesn't benefit anyone.
OK, so when you get the first thought, (in this case, relationships) let it go in your brain, but do not argue with this thought, don't even entertain it. Carry on with what you are doing and let the thought be.
If 5 minutes later, "What if I'm gay?" comes up do not discuss it mentally. Do not weigh up things like "I have a girlfriend, so I must not be gay" for example. The trick is to not even enter that cycle You can think all the intrusive thoughts you want but the important thing is not to react to them with that endless questioning. Leave it alone in the back of your mind.
If you do this, the thought become less important and they tend not to develop to the most extreme versions of the thought. By not reacting, they become like any other ordinary thought and life goes on
If you bite your nails in response to the thoughts then it might be compulsion related to OCD. It would be best to stop that if you could. If this results in anxiety, that's OK. Just know that it'll pass. I don't know if you are on medication, but that can help a lot with the anxiety so that could be something to think about.
That's OK

I think, as we get older it seems that less and less people have huge friendship groups and it's more a close knit group of friends. If it bothers you, you could always put yourself out there and try some new sports or activities. That might make it easier to meet new people.
It's really awesome you are into football/soccer though! If you can, get on a team or play more of that on a regular basis as that can be a great way to make it easier to meet and talk to new people (the exercise is great for anxiety too)