Estrace and Nervous

Here is my dimema: I was of peak fertility last weekend and took the necessary steps with my husband to try to get preg.  I feel good about us trying being that we both stopped consuming alcohol and caffiene.  I am feeling very positive about it and that we nay have made a baby naturally!  So, I am supposed to start estrace (2/night) starting on Thursday.  I am hoping to have my IVF procedure by the 3rd week of July if I am indeed not pregnant.  
So, if I am pregnant it is too early to tell.  If I take the estrace, will this affect my zygote if I am indeed pregnant?  It says do not take if pregnant right on the bottle.
My husband and I have been actively trying for a year and have unprotected sex for 4 years.  I am 35. I very much would love to pregnant from natural causes....should I take the estrace????

[Forum-M.D.-SP]

Please follow up with you REI about this question. It is his/her office that has given you your treatment plan. Good luck.