There are lots of ways to be gay or bi. Certainly your level of interest in grooming is immaterial.
I suspect some of this is physical (e. g. issues with depression, anxiety, and alcohol are not doing your erections any favors). But some is also your own thoughts and feelings.
Go to a doctor. Worried about what they're going to say? That's just words. Seriously, you'll probably find you're relieved to hear something definitive - something an Internet message board really cannot give you. Furthermore, you might be able to get some help with these other health issues. This is good beyond any issues with your girlfriend.
I urge you to contact a therapist and make an appointment. Tell him or her what you wrote here. Start talking about what you think and feel, and what sort of future you see with your girlfriend (if any; and it's okay to end it even if she is the most wonderful person on earth - you need not date forever if it turns out to not be right).
Please, I hope you will get some talk therapy no matter what the outcome is. All the best to you.