im trying to conceive

hi  i just made 21 and i been trying to conceive for the passed year and a half and its not working...my periods used to be regular before i got an abortion in 2011 and that was my  first time ever getting pregnant..since then my periods became very abnormal and i havnt be able to conceive so i need some help to figure out what i need to do to get my periods back on track, how to find out my hormone levels and what i could do to find out when im fertile...any suggestions