Hi Kimora.
I will start this off by saying that I am not as experienced as some of the other users here, but I will share my thoughts anyway.
It sounds like you are doing everything the right way by easing yourself into it, being careful not to over-pump. And I do think this is normal at first. Your body just doesn't tolerate the pressure as well as others. It is good that you are following the rule of only pumping until you feel a slight pull. But if that is still giving you trouble, either you haven't healed completely or it is just too much pressure to start out with.
I would say for now to pump only as much as needed to keep them on, whether you feel an actual pull or not (it could be that you just don't feel it as much, I am the same way). And instead of leaving them on for 15 minutes, try the 7:2 method. As in, only leave them on for 7 minutes (maybe even less if need be) and massage for another two, but repeat it as many times as you are comfortable with. Hopefully, you will be able to fit in a half hour of actually noogling without seeing those pesky red dots. There is some science behind this. And I read somewhere that if left on too long, ten minutes in some cases, the pressure can cause the cells to suffocate.
I know this must be extremely frustrating for you and I am so sorry to hear that you are having these problems. But even using as little pressure as you need is still helpful because you are increasing the blood flow, which causes the growth over time. I wish you best of luck in finding something that works for you.