That's exactly the reason my almost 4 month old daugther cries. She's also showing signs of teething, but most of the time she is jsut overly tired. I just take her to a dark room and rock her to sleep with her pacifier. She might scream for a few minutes or so, but if she doesn't take the breast and her diaper is clean-then 9 chances out of 10 she's just tired and ready for some sleep.
Good luck! I know how frustrating a screaming LO is. Mine has always been a fussy lil' girl, but we can get through this!