(Possible invade)
Well, the more thick the reed is, (1) The harder it is to play, and (2) the "fuller" the tone. As you're just starting out, Id probably go up to 2 1/2's.
Ive been playing for about 4 years also, and im only on 3 1/2's
Also, trumpet and saxophone take around the same amount of air.
If you can, try to acquire a clarinet, as the same mouth positioning is used in saxophone.
Also, clarinet is easier to play than saxophone if your switching from a non-reed instrument.
Also, what I do is put my lip on top of the mouth peice, and on the bottom (this may sound confusing) cover your teeth with your bottom lip.
In other words pull the bottom lip over the teeth
Btw, what type of sax is it? (alto, tenor, etc)
I say also alot