is it dangerous to continue to wear things if they're a little tight on your belly? i'm trying to plan out when to buy new stuff.

No, but it can be uncomfortable. I'n due in six weeks and still wear my (UK) size 12 jeans because they are stretchy, I just undo the button if I'm sat down for a long time. Maybe you should try a 'bumpband', its a stretchy elastic band like a boob tube thay you wear over the waist of your jeans but under your shirt that 'turns' your normal clothes into maternity clothes because you dont have to fasten them. you can find them online.