What to say/how to ask grandparents to help with daycare of possible TTC baby?

2. My husband will be done with school in 1.5 years and we'll be moving elsewhere for his career

3. My doctors are here and also our relatives (including said grandparents). 

4. I nanny now but am looking into a bank job.

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They constantly tell the parents of their other great-grandkids that if they lived close they would babysit all the time so that they didn't have to have daycare. 

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My husband and I have different "weekends" and would just need care 3 days max during the week, and that's not even considering that he'll be solely a student in about a year and won't need as long of periods off.

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Our push for having kids sooner are my medical restrictions. I'd want to wait until we were a tad more stable to have kids, but with my health and fertility looming over me it's a difficult decision when every year can mean detriment to my health AND means wherever we end up going I'll be with a brand new doctor and I'm incredibly nervous about that as I trust my doctor now so much, and that trust has built over several years.

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I don't know how to bring this up to them as I believe they still see us as "kids" even though we pay all our bills and have been responsible and on our own for several years (other than a little help when my husband lost his old job). They've never mentioned kids to us and honestly I'm afraid of just bursting out in tears as soon as we start talking because I'm very emotional about my fertility and possibly inability to keep a pregnancy and I'm only 21. I'm afraid they may confuse my emotion with immaturity.

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They are usually very kindhearted people, but I feel terrible asking if they would be willing to help in this way so that we could TRY for a baby. It just seems very personal and I wouldn't do it if not for my health.