Yes after 4 weeks on Lamictal, your brain chemistry will alter and you are at risk for falling into a depressive state, since your brain chemistry will change back, or a mania, too. You just never know. Dont ever stop any meds cold turkey our without talking to your doc, and trying something else. This time of year is especially bad for instability. You will need more than one med, we all do, average is 4.5 meds statistically, I take 6. You add as your symptoms dictate and change if they dont work. You have to work WITH your pdoc (psychiatrist), not just take whatever he gives you and stay on it when it doesn't work. Learn, learn, learn about your condition andt the meds available and what symptoms they are for. Lamictal is a saving grace drug that actually prevents you from falling into bad depression, it's the only stabilizer that does that. The others stop the hypo/mania. You may need something to sleep as well. Everybody (BPs) is soooo different in their reaction to meds, it's a trial an error journey to the right cocktail of them. Most of them don't work right away, like Lamictal - you should be aiming for 200 mg, that's the therapeutic dose.
You sound to me like you're in denial; we ALL go through that at first, it just sounds too horrible to accept, but your doc is telling you the truth. It DOES get worse as time goes by. I am 41 next month and Arenace, who will post, I'm sure is 43, and we both know that to be oh so true. We both started as BP II, but are now BP I. The difference between the two is that BP II is hypomania/depression and II is full mania with delusions and psychosis. You will always need medication or you will eventually begin to make bad judgements and horrible mistakes that can destroy your future, or be unable to function when the depression gets bad. BP is a physical illness like any other; it just happens to be in the brain. The brain is an organ too lol! Untreated BP leads to all sorts of other maladies, IBS, migraines, chronic gastritis, chronic neck and back pain, risky behaviour than in turn can result in death, etc. Not to mention financial problems from the spending are possible, too.
Please stay here and ask as many questions as you want, we are all very supportive here, and have been where you are for a long time.
Welcome to healing well!
Variety is the spice of life, BP is the key