I've used levothroid 17 years, post ablation; its now unobtainable. generic gives me headaches. synthroid (thyroxine) led to ab bloating, rapid weight gain, & hypersomnia; any idea why? what is next?

Adjust the dose: If the dose of thyroid medication is correct, all the available preparations should be about the same. The "bloating, wt gain" sounds like hypothyroidism, i.e. You were taking too little. The dose of the new preparation may be different from the dose of Levothroid you were on. Make sure you take the medication on an empty stomach, and not with hot liquids.