I mean, my mom still packs my school lunches! Then when I start thinking about that sort of thing I start second guessing being a parent again and I start telling myself she'd be better off without me as a parent because obviously I'm still a child and how am I supposed to be trusted to be responsible for somebody else??
hon, i'm 33 and i lived away from my parents for the past 15 years (overseas for most of those), yet when i visit my mom, she still makes me breakfast and comes to wake me up in the morning, just like when i was a kid. she'll still buy me the same little mommy presents as when i was a teen or college student studying abroad: nice fresh socks and underwear and all those sorts of stuff. she even buys that now for my OH as well, as she says he's her son too!
it's not a fact of being immature or incapable of getting ourselves something, it's our ritual and our way to say we care. you're always gonna be their child, no matter how old you are and how old they are. adults are someone's children, too (i don't know how close your grandparents are, but check them and your parents out and you'll get what i mean!).
accepting their help and care is not a sign of being an immature child. it's not like you have to refuse having your parent's love and care now that you're a parent yourself, neither they have to lose their 17 year old teen daughter just because you have a daughter of your own.
i 100% agree with Topanga on the pressure of the perfect motherhood the western culture imposes (it's not the same everywhere around the world i assure you) - and as you said, in your case you feel it even more because you feel you need to "prove" you can be a mom.
the thing is - you've already proved that, every single day ever since finding out you were pregnant. being a perfect parent is impossible - simply because we're human - which doesn't mean that anything else means "horrible". Parenting is a JOB, the toughest job ever, and as every job it has its ups and downs and things you love and the things you hate.
the thing is - moms always have much worse impressions of themselves as mothers, than as their own kids perceive them. and ultimately, it is the latter that counts, right?
i am so proud of you that you talked to your mom and that you're getting help. it will be better. you're already taking huge steps in that direction, even though to you they may seem tiny.
also, don't feel guilty if your OH offers to have Gabriella over the weekend sometimes. he's not alone on his own at his place, and if it helps you to recover a bit, it is the best for everybody. he may even feel guilty himself for putting you in this situation and all that.