"Herbal stuff" won't replace the hormones your body needs to function, so don't be too hasty in throwing out your synthroid. Most of us have felt that way, at one time or another.
Symptoms that just won't go away (such as the weight gain/inability to lose) are usually the result of poorly adjusted medication dosage.
As goolarra said, please post your current thyroid labs, with reference ranges, so we can help assess your situation.
Do you know if you have Hashimoto's?
Please post recent thyroid labs with reference ranges (ranges vary lab to lab and have to come from your own lab report).
Do you have other hypo symptoms besides weight gain/inability to lose weight?
Is your doctor testing free T3?