Fighting sleep/fussiness

DD is 3 months and almost 2 weeks old and I'm at a loss as to her change in behavior - I'm not sure if maybe she's teething early (my mom thinks she feels teeth under her gums) or if she's going through the 4 month wakeful a bit early.  She's become more fussy and though she started sticking her fingers/hands in her mouth a while ago, now she's really chomping down on her fingers.  She STTN most nights but has become the worst napper and is now even starting to wake up once a night (I know, not a lot to complain about).  I wouldn't complain except when she does wake up in the middle of the night its a screaming wake up and I hate hearing her scream/cry like that.

My mom watches her during the day and has let me know that this past week DD seriously fights naptimes and has just been generally sort of fussy, compared to the past 2 months.  I'm sure DD is probably going through a phase or a growth spurt, I just feel awful thinking she's unhappy/frustrated/in pain.  A part of me also wonders if she notices that this is the first week I'm back to work full time.  I was PT for the month of June so I was home with her 2 extra days a week.  She's too young to realize that right?  FTM feeling like a bad mommy.