First of all, congrats on being smoke free for 4 months! That is a huge accomplishment and you should be very proud of yourself.
I have good news and bad news for you...I quit smoking 15 months ago and even today, I still get the occaisional craving for a cigarette. But, here is the good news. Over time, the cravings will become less and less frequent and less and less intense. For me, it was sometime around the 9 month mark that I started to have days go by where I no longer thought about smoking. Then days would become weeks, etc., etc.
Now, when I get a craving, it lasts a few minutes and is really just a passing thought that I can easily brush aside. More like, "hmmm, wouldn't it be nice if...?" My best friend and his partner smoke and I can easily sit outside with them on a sunny day and have a few drinks while they sit and smoke beside me. I know I couldn't have done that last summer with such ease (I quit a year ago April.)
So like I said, good news and bad news. Stick with it though, it just gets easier. The thing that kept me going was remembering how difficult the initial quit was. I knew I never wanted to go through withdrawal again and that really helped me make sure I never started smoking again.
Congrats and good luck!
Feddy