Any insight on what severe nausea and headaches could be?

[Tesstr11]

Hi guys, I’m pretty desperate at this point. I’m a healthy 23 year old female and always worked out and ate right until one day I wasn’t feeling good at work. Ever since that day 2 months ago I can’t go anywhere because I feel like throwing up, I can’t eat properly or really get up and do anything or I feel nauseated. I also have daily headaches and feel lightheaded very quickly anytime I get up and am moving around. I’m basically stuck in my house a lot now. It all started with a pelvic infection, and they gave me a course of antibiotics then the symptoms never went away. They have done tests including ultrasounds and everything is normal, also done colon cleanses because they thought it was constipation but now I’m back on track... no idea what to do as I seriously cannot do anything or be normal. Could it possibly be my head?? Help!