On a practical career note, if this is a very big company like you say, internal transfers will be a possibility. Do your current job well, keep an eye on what they look for in tech support roles within the company.

On more of an LPT note, having solved the problem of getting a job, you are now faced with all of the other aspects of adulting that you were postponing. These can be legitimately stressful, even scary. Maybe talk to a counselor to help you get your bearings in your relationship with your girlfriend and with your parents. Not that I think you sound mentally ill, but some counselors also have expertise in normal but major life changes. It’s like a very professional life coach. Avoid those life coaches that are basically just fronts for pyramid schemes, though.