Hi...I think that the best thing for you to do is to get in touch with your doctor and discuss this with him to come up with a plan on how you should go about resuming the med without it causing you any problem. Lamictal has a great side effect profile, however, there is a risk of a significant rash you can get that could have you ending up in the hospital if the med is increased too fast....that is why the starter pack was created so that the risks would be minimized. I believe that you start out with 25mgs for a few weeks then up to 50mgs for a certain amount of time and slowly increase as the pack directs you. Now if you took the first few weeks of 25mgs and then stopped (I think that the window of time you can stop without having to start all over is 48hours) you shouldn't go taking 50mgs or you could be putting yourself at more risk of developing the rash (Steven Johnson Syndrome). Like I said, it is a minimal risk but you will increase that risk if you do not take the medication as perscribed.
Lamictal is a great med but takes time to get up to a therapeutic dose because of how slowly it is titrated. But when you finally get to the right dose which is somewhere between 200 -300mgs it works very well. My daughter is on it and is doing quite well. There aren't many meds like Lamictal that are weight neutral and address both the manic and depressive side of Bipolar. So I wouldn't exhaust it as an option and talk to your doctor about what you should do to resume it. It may just involve him calling in a script for some 25mg tablets to get you back on track.
Hope this helps...good luck ~ Goody