Today We Had A Blood Drive At Our School. I

Today we had a blood drive at our school. I went to go give blood and when they stuck the needle in my blood was flowing as normal but after a couple seconds no blood was running through. The lady kept trying to help and get the blood to flow again but it wouldn't and when it did it was slow. When she looked in the bag there was big clots in the bag. I notice when I am on my period that I have these clots as well. I was wondering if this was normal or if it was something I should worry about. Is there anything could do to help this and should I go see a doctor?