I was diagnosed with Hypo around age 22, and am now 33. Like you, I have also battled with gaining weight easily and not being able to lose it. In April of this year I ended up having my thyroid completely removed because of growing nodules.
Knowing what I know now, this probably could have been avoided. So many doctors do not treat you based on how you feel, only by one simple lab test. And the ranges have changed for optimal thyroid function and many doctors (and labs) have not adopted the new guidelines. Your TSH should be between .3 - 3.04, as recommended by the AACE in 2003. Most labs will give the "normal" range as .5 - 5.0. So if your lab values fall above a TSH of 3, you should be given more hormone. If your doctor is like most and doesn't recognize this, find one who does! That is what I had to do and I feel so much better. I was taking hydrocodone daily for aches and pains, I was tired a lot, had no sex drive and had "brain fog" at times. Since getting on a higher dose, all of those problems have gone away! You wouldn't believe how many symptoms we have that are related to thyroid and doctors don't recognize it. A good doctor will also check your T4 and T3 levels, not just TSH.
I highly recommend reading these two books. They were recommended to me by an online support group and they will shed so much light on our condition. Everything from foods that are bad for us, to related conditions, supplements, and the different types of thyroid hormones.
What Your Doctor May Not Tell You About Hypothyroidism - Ken Blanchard, M.D., Ph.D.
Living Well With Hypothyroidism - Mary J. Shomon
You can find these books on Amazon (used even) for little cost. They changed my life and gave me the courage to take control of my condition, by seeking out a doctor who cares and listens, does thorough testing and got me in the optimum range.
So, to answer your question....No, not if you are on the right amount of hormone and have a good doctor to monitor you regularly!
Best of luck
~Melissa in FL