Strongarm66 is right. You need to find a carry pistol that fits you best.
There are lots of options here. First pick a caliber. This is a debate in itself. Choose the largest caliber you can proficiently shoot. In other words, if you can shoot a 9mm well but can't hit shit with a .40, stick with a 9mm.
Go to a store (or gunshow) that carries a variety of pistols. Weigh the pros and cons of each one. Pick them up and see what fits you best. Some good ones to look at are (in no order) are- Glock, Smith and Wesson M&P, Springfield XD, Sig's, etc. (I'm sure there are others I have forgot)
Now you need to choose a holster. How will you carry it? Inside the waistband, middle of back, shoulder holster, ankle holster, outside the waistband, etc.
Leather, kydex, nylon, holster? Belt holster or paddle?
And finally- practice, practice and PRACTICE!!!!!! You can buy the best equipment money can buy, but if you don't practice, it won't do any good if it is ever needed.
Me personally, I carry Glocks. I carry a Glock 23 in the winter and a Glock 27 in the summer (both .40's). I carry them in Blackhawk SERPAs set up with a paddle attachment and a spare magazine on the weak hand side. This platform works best for me.