I don't think what you are referring to was a blood clot. Your veins develop scar tissue from being stuck so much. My veins were so bad they had to put in a PIC line. Your bad headaches could be the result of your high blood pressure. Every time my blood pressure went up, I would get a terrible pounding in the back of my head and sometimes the top of my head would feel like it was going to blow off. It's a miracle I didn't stroke out many times.
Your doctors don't speak English?? Where are you?