GO FOR IT! You'll be fine!

If staying home with bubs is important to you now, your feelings will intensify 100 fold when bubs is here. I can tell you there is nothing worse than dragging kids to childcare and then work yourself when you just don't want to.

You will be fine on a lower wage for awhile, because you are young and don't have a massive pay packet to miss. It's fabulous training financially.
BUT, use the time at home to keep studying and educate yourself. I used to do a short course here and there, pick up a day or two work here and there.
If need be you can always pick up a part time job at night. My GF does 7pm-11pm 3 night a week, her DH is home with the kids anyway and the little extra helps.

By the time I was ready for full time work, I bounced straight into a well paid job and went overseas, upgraded my car and bought a house.
I since went back for more kids, so I'm mainly at home. I have lotsa bills to pay and I really do miss the $$$, but I can't leave them in childcare!
Nothing can replace those first few years at home, big screen tv's and a 2nd car just don't rate in comparison.

You will be fine!