Is it normal with hoshimotos disease for your thyroid to stay enlarged for months after being treated?

Yes: it may remain enlarged for the rest of your life. What's important is it's function not it's size.

Yes it is normal.: Hashimoto's Thyroiditis can present without any enlargement to variable degree of enlargement.It can present as thyroid nodule -single or Multiple.. If you been treated with Levothyroxine/Levoxyl/Synthroid it may help to reduce the size of gland or it helps to prevent further enlrgement and small % of cases it may get to normal.It may need to adjust the dose of treatment .