I'd like to flag up that your GP suggested in a phone call that you JUST stop taking it! Obviously I don't think you would just go cold turkey, but really.......
Have a really good google around on prozac whilst pregnant, and I'm sure you'll find loads of women who've been fine; then go and see your GP (not sure why you don't want to, do you think he's OK generally?).. and find out whether there is something else you can try if nec. Personally, I'm in my 29th week, and I started slowing down my dose at 12 weeks ish... I found it impossible to start withdrawal in the first trimester but it worked a charm thereafter. I'm still on the tiniest dose ever (2.5mg/day from 15mg of escitalopram)... and hope to be finished in the next month; but expect to start right back up again, probably with venlafaxine, when I've delivered.
To go back to you - he sounds like one of two kinds of GP (in my long and bitter experience). Those who know enough to see past the two line edict that is currently in the drug books, and have read up on current small studies showing actual hard evidence and those who don't...
OK, I've just seen a new study(this is my area of interest!)... but the anecdotal stuff is very interesting too if you want to look for it..
"The antidepressants included in the analysis were: bupropion (113), citalopram (184), escitalopram (21), fluvoxamine (52), nefazodone (49), paroxetine (148), mirtazepine (68), fluoxetine (61), trazodone (17), venlafaxine (154), and sertraline (61). Conclusions: As a group, antidepressant use in the first trimester of pregnancy is not associated with an increased risk for major malformation above the baseline. In addition, no individual antidepressant was associated with an increased risk of a specific malformation"
www.ncbi.nlm.nih.gov/pubmed/19321030?ordinalpos=2&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsP anel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum