I just can't do it

I have a hard time with masturbation. I usually start by rubbing my clit through my underwear, but that only does so much. Plus, sometimes I can barely feel it and that makes me wonder if I'm actually touching the right spot. I've looked it up and I'm pretty sure I am, I just don't get all the pleasure that everyone else says they're getting from that spot. I've tried other things like riding a pillow, and that still hasn't worked well for me. Using a showerhead feels nice but only for so long.

I've talked to a few friends about this because I know they masturbate and I know they can finish themselves off. They all use clitoral stimulation and one even uses vibrators. I've tried taking their advice (one told me about pillow riding with a towel), but it wasn't very successful.

I try to relax the best I can, but I can't stay relaxed and I think that might be one of my problems. Do you think I'm not getting turned on enough beforehand?

I'm 15 and not sensitive or anything, and I could buy a vibrator from Spencer's or Rite Aid if I really wanted to.

What advice can you give me?

(PS, sorry for writing so much!!)