18 yr old male with problems

Hi, I'm 18 years old, I've been athletic all my life and never ever had any problems with anything up until now, I'm mostly healthy and I will admit have been drinking alcohol and smoked some cigarettes from time to time with my friends. Recently I've gone to the doctor several times with a funny heartbeat that made me uncomfortable and would give me times when it went really fast for no obvious reason, I also had a really nasty cold at the same time that started a few days after I noticed my heartbeat and I got headaches up to the point that I felt like passing out from moving around too much. I had several heart exams and my doctor said I have a viral infection that somehow dilated an artery going to my heart, that was a week ago and he said I'll be feeling better within 2-3 weeks, he also gave me Xanax since I was quite worried. After that I've been feeling better and I've pretty much felt normal just that I still got mild headaches from moving.

Now yesterday just before I went to bed I was just sitting down by my computer and I felt a pressure on my head like someone was pressing down firmly with their palm on my head. I was unable to sleep, I just finally(3pm) managed to get some sleep but I still have pressure in my head, also it feels like my head is numb, I can barely feel my head when I scratch it with my fingers.

These last 3 weeks have been driving me crazy and at first I was terrified I was having heart failure and now I'm scared of an aneurysm or a brain tumor and I'm wondering if this constant head pressure and numbness is caused by the viral infection my doctor said I have or If someone else could've affected me.

Any help/tips is much appreciated