wtf why pls help bby probs

My baby is been so whiny lately. She usually lays down, I pat her back & she's out. Now all she does is squirm around & cry. She'll suck on the pacifier for like 3 minutes spit it out & repeat because I'll keep giving it back. She full, burped, dry diaper, bathed, am I missing something? She's only 3 months but this change is killing me. I'm a single mom, worked all day, & have homework to do every night. The lights are off to set the bedtime mood. I'm getting really frustrated with her. I know she's only a baby but I'm going nuts. Any suggestions please!