C.S.
No, you are a mom and still human! We all have thoughts we are less than proud of, oh believe it. I have that feeling sometimes with a healthy *(but insanely rambunctious/defiant:) two year old (2 and four months...) so I can only imagine the extra stress with developmental delays.
Speak up and get time outs for yourself- don't ask, TELL your husband (or boyfriend, I don't want to assume ha) you will be doing such and such and when so he can help. I do this and finally made a 'standing date' activity to at least have something to look forward to.. and make it less likely I let a week, then 2 weeks go by and I am back to not taking time off for recharging. That so easily happens. This is true for all moms but especially moms with extra worries with their child's development. This all sounds common sense and it is..but bears repeating since so many women seem to still not heed this advice.
I second the support group for moms in your situation, too! A mom going through similar scenarios *gets* it, and you will be able to confide that much more in them and not *edit* yourself for fear of being judged. A mom with kids going through the same thing will be invaluable to you..hanging out doesn't have to be all about swapping practical tips either. It can be just socializing too. Meetup.com has groups, you can create one too easily if none exist that you like.
I really think the extra strong parents get put in charge of kids who need a little extra patience/have different developmental needs. So many people lack the coping skills for that and while it feels like you are floundering you're doing better than many who'd just snap and be less than understanding parents. So kudos. And go do something nice for yourself now.:)