My iPhone 3GS wifi wont connect if I leave the house with phone and come back

So my iPhone 3GS (which i bought in December 2011) (out of warranty), will not connect to wifi.. My phone already has problems (randomly i lost my network and it always stuck on No Service, which doesnt allow me to make calls or send texts ). I have a backup phone that I use, but I still use the wifi on my phone for playing games, listening to music, etc. (basically using it as an iPod). But recently, I started having problems with the wifi, every time I tried to load a page, the wifi dropped and it did this constantly. After a while it quit dropping, until one day I left the house with my phone and when I came back I saw that I was unable to connect with the wifi. At home the wifi works, but whenever I leave the house with it, the wifi doesn't connect for a while. I stopped leaving my house with the phone so this problem stopped for a while. But today I ran into a new problem, I did not leave the house with the phone, but simply turned the phone off, left it at home, came back after 2 hours, and turned it back on and was unable to get wifi. I reset the network settings a couple times, but still when I try to connect to a network.. I get "Choose a Network... Other.." with no networks at all showing up. I've been waiting 2 hours yet nothing shows up.. Any help?