I would definitely eliminate mechanical issues as the source of the problem first. If you have a repair shop nearby, most shops will give you a free appraisal. Otherwise, its easy to look for leaks on the lower notes yourself. Throw a small but bright flash light down into the bell and then cover the top of the bell with tin foil or some other means of sealing in the light. Then turn off the overhead room light and look at the C# pad seal as is and also slowly close B, Bb and low C. If you see any light leaking out on any sides when closing with light pressure then you have leaks. it could also be leaks further up the horn that are causing you grief with your low notes, but that's a good place to start.

Once you've either eliminated or fixed mechanical issues, let us know how you're doing.

It does take some time to get your chops back and if you're questioning it, I would also recommend taking a couple private lessons with a quality teacher who knows how to teach proper embrasure. Getting it right from the beginning is well worth the small effort upfront to avoid the painful process of unlearning bad habits down the road. Best of Luck!!!

Cheers,

     Mark Overton
     www.saxquest.com