I completely understand where you are coming from. When I was 19 and my BF (now hubby) was 21 we were told I had severe endometriosis and would probably never have children. They advised if I wanted kids to start trying as soon as possible because if I was lucky enough to have any the window wouldn't be open very long. At that time we were living with his parents (I was living with my mom, she had to move a few hours away and we didn't want to be apart so his family let me move in with them.) I wanted to have kids SO BADLY and my BF did too, but my biggest fear was not being able to support ourselves all on our own. We decided to wait. As hard as it was, knowing I may be throwing away my chance at a family, we waited. We finished school (opting for careers needing only a year training rather than finished university), rented our own place, got jobs, and once everything was settled we decided it was time. And when I was 22 I got pregnant with my son.
Every day I am thankful that I waited those 3 years. In the big picture it's not that long to wait. Now we have a big house, we can support ourselves financially, and we don't have to worry about money when my sons asks if he can play basketball or soccer or hockey. Had I not waited I think my journey would have been 100 times harder.
And I will admit it......if I knew I could still have have kids another 5 years down the road, I would have waited longer. Part of me wishes that we had had some time to enjoy our financial independence on our own. We never got to travel until after he was born, and apart from a one week honeymoon we have never traveled without our son. We can never go out at a moments notice and join our friends...things need to be arranged in advance with a sitter.
It's not an easy life, being young with kids (I'm 25 now...I hope that's still young! lol) but of course, my son is the light in my life and makes it all worth while.
Really think it through before you make a decision. There is the good and the bad, the pros and the cons to weigh out. I'm not saying either decision is right or wrong, only you two together can decide what is right for you. But as for those maternal instincts...holding off may be hard, but it will make it that much sweeter when it is your turn.
Best of luck!