Pregnancy & Prescription Drugs

I am not TTC yet, but I feel like with every sexual encounter I have with my partner I am setting myself up for the possibility of becoming pregnant.
First of,
I am a 23 female, relatively healthy.
But I do take prescribed medications everyday. I have finally cut down to 3 which are,
Lisinopril (high blood pressure due to genetics)
Pristiq (anti depressant)
Ambien (sleep aid for my insomnia)
I like to take a pregnancy test every 5 days before I expect my period so I can catch anything as soon as possible, as I do not know what these medications do to a forming baby. I am more concerned with a life that isn't even here/ hasn't even been thought of more than myself. 
Ladies, are there safe drug alternatives for these medications? Should I try to ween off as early as I can? Lisinopril is my major concern as in it is very important for my body to work correctly, but can be damaging on an underborn baby's body. 
I'm trying to be a responsible mother even before my child is conceived. Please help!