Good job for being so persistent with attempting to test your kitty.

When we were first starting out we also had great difficulty getting enough blood to test... it was frustrating but we learned a lot. so here's a few tips for you
1. We always gave the cat a low carb treat whether we got any blood or not... You want your cat to see testing as a precursor to yummy things and extra attention and petting and love.
2. We learned that if the ear was not warm enough there wasn't blood available to collect. We put about a 1/4 of a cup of uncooked rice in an old sock. We then tied the sock closed with a piece of string. Be sure you leave a little space in the sock so you can wrap the ear easily with it to warm it up. We heat the sock in the microwave for about 25 seconds. Always test it on your wrist like a baby bottle to make sure it's not too hot. Then wrap the ear in the sock and massage. When the ear is warm, it is so much easier to get blood.

3. Know that there are few pain receptors in the ear so it's mostly a painless poke for the cat. We do use neosporan on the ear partly for pain relief but also so the blood will not disappear into the fur which means another poke is needed.

4. keep poking in spite of seeing few drops of blood. the ears "learn" to bleed with repeated attempts.
Hang in there. It does get easier.
I hope this is helpful to you