Veins battling to stop bleeding after donations

Does this happen to anyone else?

The first time it happened was around this time last year, I was sitting there after my donation waiting for my husband and I just felt my arm go warm and when I looked there was blood everywhere (it's approaching winter so it's cold).

No problems again, then the first donation of this year when I took off my cotton ball there was quite a lot of blood on it.

Last time, I had to sit there with my arm in the air for 15 minutes and they kept having to wipe alcohol on my site.

Today it didn't bleed as much initially, but then I felt my arm go warm at the shops again afterwards and when I looked, I was starting to bleed through and had to go back to them (luckily I was at the shop right next door).

I do swop arms, I wait the necessary time between donations, I don't bend my arm afterwards.... Not sure if this is normal or not.

For reference I am anemic (they blood bank knows and my iron is tested every time, plus they give me iron pills), I have donated around 50 times.

EDIT - if my iron is too low I get deferred for three months. Has happened many times but as long as my iron is above the minimum requirement they let me donate.