1. Remember that you have a problem asking for help and that your fears are likely more extensive than realistic. So it is just emotional fear rather than a real cue that you are overstepping bounds. You haven't yet received confirmation that someone thinks you are asking too much, and they haven't been yet given an opportunity to offer that kind of feedback, so you don't know.
2. Relationships are two-ways streets. Not only do you give to others, but others need to be able to invest in you, if it is to be a close bond. So not asking for help will diminish your relationships.
3. Just because you ask someone to do something doesn't mean they are obligated to help. They have the choice and responsibility to say no, if they can't help you for whatever reason. And you need to be okay with that rather than facing it as rejection.
Likewise, do you ever feel compelled to help people just because they ask? How good are you at saying no to things you just can't reasonably give? Maybe you are forgetting about other people's ability to choose for themselves because you yourself tend to over-give even when you can't reasonably give or don't want to give? Just something to examine...
These are the kinds of ideas that help me. I don't know if any would help you, but there they are, I hope something can resonate. All the fears you describe are things I've experienced too, but I basically try to "think" my way through it to get some firm footing.
"Hey Capa -- We're only stardust." ~ "Sunshine"
“Pleasure to me is wonder—the unexplored, the unexpected, the thing that is hidden and the changeless thing that lurks behind superficial mutability. To trace the remote in the immediate; the eternal in the ephemeral; the past in the present; the infinite in the finite; these are to me the springs of delight and beauty.” ~ H.P. Lovecraft
Hm i actually gradually learnt to do this sometimes in response to the very many ISFJ profiles online stating in no uncertain terms that it is an ISFJ weakness to suppress their own needs/wants. I tell myself and the other person that I'd rather talk about it now (even if it's stressful/discomforting) than to fight over it in the future. At the risk of sounding like I'm speaking from an entitlement mentality, I'd like to say that I feel it is rarely the case that an ISFJ asks for more than they deserve.