girl, i can totally relate! you may be experiencing agoraphobia, imho. basically a fear of going out. i have a fair dose of that and i have to make myself go out often enough cause the fear just builds up so intensely if i don't 'expose' myself to the elements. when i was in that funk, i'd first go to a place that had people but was rather not intesnse, like barnes and noble. btw, i'm bipolar too. i also have trouble sometimes, when the bp is acting up, driving. i'm so distracted it's not safe for me to drive. so those days i stay in for the community's sake. lol. i just can't concentrate and feel like it's too much stimulus at one time.
do you have a therapist? i'd run this by him/her. sometimes when we don't feel quite right, it's an indicator of something with the bp. if you talk about it to your T you can possibly thwart off an episode. definitely if your friends are noticing a change it's probably true. keep us posted, will you?