Well, I can't tell you anything for sure. I know it can be more difficult to conceive if you're underweight (although I don't know your height or build so couldn't say for sure if that's the case). However, you will naturally gain weight during the course of your pregnancy. I know several people with smaller builds who successfully conceived and carried to term. There are several things you should consider if you're trying to become pregnant - starting to take certain vitamins, like folic acid, before conception for example. I'd make a list of concerns and questions, and make an appointment to talk to a professional in that area before actually making the attempt. If you're on any psych meds, that could also be a concern. So you'd need to plan around that as well. Good luck.