Over the past 3 years I've been gaining weight probably because I don't eat right or exercise much, as well as problems with absorption of levothyroxine. I weigh 130 pounds now and I would really like to lose about 20 pounds over the next 5-6 months.

Take Synthroid on an empty stomach with a full glass of water. Wait at least 1 hour before eating or drinking anything but water. Wait at least 3 more hours before taking any supplements: vitamins, minerals, or fiber.

At your size, a healthy weight-loss goal is .5 lb. per week. I have Hashimoto's, and I lost way more slowly than most MFPers. So be patient!

Log everything you eat & drink accurately & honestly. Read this: http://www.myfitnesspal.com/topics/show/1080242-a-guide-to-get-you-started-on-your-path-to-sexypants

FYI, it took me a whole year to lose 20 lb. Everybody's different, so maybe you can make your goal of 5–6 months. But if you don't, it's not because "ur doing it wrong." Celebrate however many pounds you lose by then, and keep going!

Hey we could be twins (except I'm much older). I'm 5'1" and hypo too. My weight crept up to almost 150! I am on armour now and am down to 125. My goal is 110-115 or whenever my blood sugar becomes comfortably in the normal range. The medication tends to increase blood sugar a bit, and I am just at a borderline a1c number right now.
I lost at about 1lb a week as soon as my dose was stable. Before that I couldn't lose more than a pound a month on a vlcd!
Right now I am at 1500 cals a day, losing 1/2 lb a week and that's good enough. I could eat more if I exercised more so I need to work on that.

Eta: oh and I guess that answers your question! First get your dosage right otherwise nothing will work, then it's mainly about the diet to lose the weight and lastly exercise will enable you to eat a bit more. However, synthroid didn't work for me so I'm happy to be on armour.

in to follow (I'm also on Levothyroxine)

I think editorgrrl got the basics of the difference. Armor/nature-throid is from natural dessicated thyroid -- of either pigs or cows - so in addition to T4, it also has T3 and the other thyroid hormones. My doc says that he doesn't necessarily know why some patients respond better to it, but that they merely do -- he's found in his practice this to be particularly true for those with autoimmune thyroid issues like Hashi's.

Natural dessicate thyroid has been around for a long time and is what they originally treated hypo with before the synthetics were invented. The con against them is that their not as consistent or pure as the synthetics, but this is greatly debated. Some say this is no longer the case and the difference is now negligible. Others say that a lot of endos get kickback from synthroid and the drug companies, so they're biased in that direction. Personally, I think it's probably a little bit of all those things.

I think you can dose either based on meds/bloodwork, but the type of docs that tend to prescribe their patients Armour/Nature-throid (or you don't have to super fight them over it) tend to have a more holistic view of the patient. That, essentially, the patient is more than his/her lab results and they recognize that those certain things may be "within range", they may not be optimal for any given patient, so looking to clinical symptoms is just as important, if not more so, than blood tests. After all, how many would be going to their doctors for thyroid treatment at all if they didn't have any symptoms? At least, that's my doc's view. Blood tests are important, but their only one weapon in the arsenal and that clinical symptoms should be given considerable weight as well.