Whoa hold it right there. You are not sure if you even want kids! Why are you letting him pressure you?
Kids put a bomb in your current life, I know I have 2. It will put your life under stress so if one or several elements of it are not up to scratch it will creak and groan and those problems will become more stark, resentment sets in etc. Having a child is he biggest test, it's when you find out truly who you both are, whether you work as a team and what you are really made of. Some people take to parenting like a duck to water, some people get by and some people just survive.
Have you asked him WHY he is so desperate for kids suddenly, because there are a lot of reasons that aren't great... Such as family pressure/ cultural expectation/ sibling competition etc. I actually think it's quite unusual now for men to want kids, but someone will come along and say NEM!
A great many women find out AFTER having kids their partner is a lazy self centered person who thinks raising children and the mental load of doing it as well as the physical load is ',women's work'. Swerve these men, it only gets worse and you will wind up hating him. I'd probe a bit deeper on what his views on women really are, his own childhood (what role did his father play-would he be different?) and how he plans to raise his future kids right through to adulthood, is it the same way you would do it or will you have to compromise and are you both prepared to do that? Also a very important question is...WHY did he break up with his former fiancée...I'd be very tempted to ask her the same question! They were going to get married and one of them backed out. WHY? And why is he now not bothered about marriage when he had proposed to her...it's a bit fishy.
Also you need to do some work on yourself first. You say you are in debt, great clear it quick but HOW did you get this way in the first place? If you are only just making ends meet things will get much much worse if you have a child so need to focus on boosting earnings first. If it's that you bought lots of unnecessary things, you need to learn to budget as a mortgage and a child are both massive long term financial commitments and you will have to go without the things you fancy (unless you are loaded!) to service both commitments. It's estimated the current cost of raising a child to 18 is circa £200K at today's money. And it costs more if you have to do it alone (which entirely isn't fair!). You worry about everything to do with your child, last thing you want is relationship worries or financial guilt on top. How will you continue to work (assuming you haven't preagreed to live off your partners income or parental handouts?). What is the childcare like in the area you plan to settle in? Find local Facebook groups and ask what nurseries or child minders are around and then find out how much they charge and what help would be available to you. My youngest's nursery cost is £94 a day in the South East (not London) for example..
I hope this serves as some common sense talking, you sound like you have your head properly screwed on anyway to be thinking about this now and not just accidently getting pregnant...which is how I did the first time, wish I could go back in time and tell myself these things! It's worked out ok in the end but could have been easier, less heartbreak and less stressful times with prior planning.