Ttc 2nd childi

So me and my husband have a beautiful 4 year old daughter. Now we are really ready for another child. There is an age gap of 14 years with us. I am 25 and he is 39. Although i say were ready for another child, i haven't actually been on any contraception since i had our daughter 4 years ago. But now we really want another baby and im starting to worry that after 4 years of being on no contraception.. Why haven't i caught on yet? I mean i caught on within the first 2 weeks of trying with our daughter! Should i be concerned? Should i see my doctor to see if everything is okay?