Blood work

So every time I go for blood work at my fertility clinic (which is a lot since I’m taking letrozole and doing timed intercourse) they always struggle to find my vein and sometimes I feel dizzy and faint. Does anyone else have this issue? Any tips to help make it easier to draw blood? I drink soo much water the day before and morning before I do, I shake my arms around on my way in, I showered in the morning to try and improve blood flow. I’m not sure what else I should do lol. Any tips would be great because every time they go through my hands they bruise up, and I end up getting jabbed so much in the arms.