Absolutely agree with the above posters especially the parts about being financially ready and living your married life first as a couple for a while without a child.
annie is right. get married first and save money. you are very young. you have plenty of time to have a baby. make the future bright for your baby by becoming financially a stable and prepared. a baby will grow to a toddler and a child then a teenager. they do not stay babies for long so you need to be ready for raising a PERSON.
Frankly, the best time to have a baby is after the couple has been married a while and had some fun together without a baby. Get the money together, your jobs set, your patterns set with each other, go through a few Christmases and birthdays as a married couple, cope with the in-laws and their expectations and demands, then have the baby. The reason I say this is because it can be a whole different dynamic to be married (different than when unmarried and a couple), and you want to know what that is in your lives together, before adding the stresses of parenthood to the mix.