Advice needed

So in July, my boyfriend and I are going to start trying for our first. I am only 18 (will be 19 in June), but my doctor said that I may have limited chances in the future so we have decided to try now. However, our time is limited to 20 days to a month due to him going away to college across the country.  How can we be sure to get pregnant within this times I know the basics: prenatals, watch weight, etc. but is there anything that I could be missing or need to do? Any medicines I could take??