Having a bit of an existential crisis.

I was being super cranky when John got home from work yesterday. There could be any number of reasons: I was trying to make plans with Sarah yesterday to take the girls to the park--it was such a beautiful day and I just REALLY needed to get out of the house! She agreed and then kept postponing it. She finally texted me and said her sister had just called and said she really needed her (Sarah) to come pick her up from work. I was pretty mad. Not only because I had really been looking forward to going to the park with the kids, but also because she freakin' does stuff like this all the time! She's SO undependable! Right after I had Olivia, I was late everywhere and for everything and Sarah was like "Yeah, now you know why I am the way I am!" Well...yeah...Though I DID have a newborn baby and now that I've been at it for 6 mos we're never (okay, very rarely) late for things anymore. Because I've adjusted. I know how much time it will take to get me and Olivia both ready, pack her bag, pack her in the car and GO! I've got it down to a science even. Sophia's almost THREE and Sarah STILL doesn't have her stuff together! She's always been like that! Anyway...it just really got to me yesterday, I was so totally disappointed. Then John got home a little late because he had to stop to run an errand, which is fine, but I STILL didn't get to go to the park to play with Olivia because it was dark (or getting that way) and pretty cold by the time he got home. I think I'm having more "Baby blues", or something. It's really hard because right before I got pregnant I got diagnosed with pre-menstral dysphoric disorder, but didn't do anything about it because then I got pregnant and those hormones (I guess) were overwhelmed with crazy preggo hormones. I wasn't really DEPRESSED or angry when I was pregnant, I just had these moments where I would cry over weird things (like Fancy Feast commercials and the movie Space Cowboys). Since I'm still breastfeeding Olivia, I haven't gotten my period back yet, but I'm starting to get the PMDD symptoms back again--I'll lose control and rage at John, or get super DUPER depressed and...well....I prolly ought to go on anti-depressants, but I'm pretty hesitant to do that because I don't want to stop breastfeeding Olivia (at least until I get a job) and also because anti-depressants lower your sex drive and John and I are already having problems with that because breastfeeding does that too. That, combined with staying home all day with Olivia and feeling so lonely, has REALLY made me depressed. Lately it's been hard to even get out of bed and do things. I feel like I'm not really full-filling my potential, I feel like I'm not contributing to my family and I just don't want to look back on my life and feel like I didn't really accomplish anything. I was talking to John about it last night and he pointed out that I have a great life--a life that a lot of women would love to have. I have a great husband, a beautiful and healthy baby girl. We have our own house and wonderful friends and family. And all that's true and I am VERY thankful for it. I just feel like I need to make a difference in the world. I know I should focus on being a good wife and mother, and I definitely want to do that, but I want to be a good role model for Olivia, I want to HELP people and make a difference to the world at large. I would love to do some volunteer work, but that's not really possible with a 6 month old baby. I mean...I know there's prolly a way, but I am really just trying to keep my head above water taking care of her and the house (and quite frankly the house is NOT where it should be, especially since Olivia is going to be crawling soon). I just don't know. Some days, it's just really hard to get out of bed and face the day. I do, because I have to take care of Olivia, but if I didn't have her, I'd be in a MUCH darker place than I am right now....