I Just Got Up Off The Coach And Walked To

I just got up off the coach and walked to the bathroom. About 5 seconds after I got up I started to feel dizzy and had an intense pressure feeling in my head. My vision went fuzzy,I felt light headed, and I grabbed the wall. I was unable to keep my balance and ended up falling. It felt like I was about to pass out and everything happened slowly. This episode lasted 15seconds and now I feel fine. I've been sick with a sore throat for 2days. I'm an 18 year old male and am generally healthy. This type of thing happens to me every other month or so right after I get up from a sitting position but It has never been this extreme. Usually I just feel light headed and my vision is slightly blurred for about 5 seconds. I'm wondering what the source of these issues could be and if I should see a doctor?