We Have Been Trying To Conceive For Over 2 Years

We have been trying to conceive for over 2 years our 3rd child, we go to a RE and am ovulating on dexamatheson and femara. This is our 4th consecutive month in over two years of ovulation. Again a negative test. I will be traveling out of the country to the amazon area a week prior to ovulation. I have been prescribed doxycycle to start taking prior to leaving and for four weeks to prevent malaria. I see Doxy cycle can affect birth control, can it affect the fertility drugs? and if conception were to happen would it have an effect, as the drug would be completed by the time we would know if we were pregnant?