as others have said, breastfeeding doesn't necessarily mean you can't get pregnant. I exclusively breastfed both my kids and my periods returned 6 weeks postpartum with both.
Only you can know whether it'd be right for you to stop breastfeeding for those reasons. But, seeing as you asked, I personally think it'd be a shame if you did. As you no doubt know, breastfeeding comes with lots of benefits for the baby. It helps protect against lots of things, from obesity to colds, asthma and even some cancers. I know it's not a popular way to put it, but by switching to formula, you would be increasing your baby's risk of those things. So for me, if breastfeeding is working out, it's not worth giving up for anything. You'd only be exclusively feeding for another 2 to 4 months anyway and after that, you pretty quickly get more freedom. I know that may sound like a long time, but it really isn't, and would make a big difference to baby's long-term health.
DISCLAIMER: I'm not judging anyone who can't breastfeed or even chooses not to. I'm only answering Lucy's question because she's asked for people's views on the topic. Obviously every mum has to decide herself what's right for her baby and herself.