Nursing cues question

AndromedaEclipse

We think DD is going to be teething here shortly.  She hasn't cut teeth, but she chews absolutely everything and drools everywhere.  I nurse on demand, so it's hard to tell when she wants to nurse and when she just wants to shove everything in her mouth.  I don't know if she takes the pacifier when she cries because her gums hurt or if she's actually hungry. 

If we're at home, I'm more likely to try to nurse her every time she cries.  We're away from home frequently during the day (8:30am-12pm or so), and I tend to give her the pacifier until she refuses to take it because I don't know if she's really hungry or not.  I work from 4-7 pm, and DH gives her one 2-3 oz bottle in that time.  I'm worried that she's not getting enough to eat.  I feel like a terrible mother because I don't even know when my daughter's hungry.  She's been waking up a lot at night to nurse lately, and I can only attribute it to not getting enough to eat during the day.

What nursing cues can one look for in a teething baby?  How often should a four month old be nursing?