Should I take diet Pills before conceiving??

Hello Ladies,
Okay so I am a mother of a beautiful 4 yr old girl ever since then I haven't really taken care of myself. I have gained 55 pounds since then and that is no longer baby fat, obviously it's me!
Anyway getting to the point my husband and I want to concieve hopefully by July 2015 but are no yet trying and I really want to loose weight. My husband and I are hopefully going to have two children more and I know I won't get back to my regular wait for a while. I'm already out of shape and I'm really worried for how it will be after giving birth!.. 
I know this is silly and doesn't make sense but having no time for myself or workouts I do still want to remain healthy/fit especially for my family and myself. Maybe it's jitters or being nervous about going through it again but even though I should have worried about is long before Im really worried now :/..
This would be the first time I do something like this but..
Here is the question; is it okay to take diet pills (garcina) even though I will most likely start taking prenatal pills starting next month since it's three months before conceiving?