HELP! Large lump in my left breast. Also, could I be pregnant?

Hi. I recently started getting a lot of pregnancy symptoms such as nausea, vomiting(which subsided in about 3 or 4 days, I get nauseous every now and then but don't have to vomit), dehydrated, moody, being hungry a lot, and I've had a steady cramp/pain in my lower left abdomen for a little less than a week now, and of course, swollen/aching breasts for about a week or more. However, my right breast is just swollen and squishy but my left breast is still slightly smaller than my right. Not to mention my left breast has a lump in it about an inch-1.5" big to my right of the nipple, and it is sore. I have taken 2 pregnancy tests I had left from a 3 pack box, one I took about 2 days ago and the other I took last night. Both read "Not Pregnant." However, the expiration dates printed on the wrappers were "11/2012" and well, as you can see from the date, it is now 11/2012. I have a very very irregular period to say the least, and its hard to know when to take tests or how much longer to expect I will miss a period. My husband and I had sex 3 days ago, 5 or 6 days ago, and about 2 or 3 weeks before that. My last period was about a month and a half ago, give or take. I am also just now feeling my lower left stomach and it feels as though there is a small knot in it as well, about an inch below my belly button and another 2-3 inches to my left of my belly button, it feels like it is about 1.5-2 inches big and is exactly where my abdomen has been aching. So, my questions are, 1.) How can I know when I should take another test? 2.) Could the tests being so close to an expiration date give me a false negative? 3.) What could the lump in my breast be? A clogged milk duct? And what should I do for it? 4.) What could the ache in my lower stomach be? And ultimately the biggie- 5.) Do you think I could be pregnant? Any and all answers are appreciated beyond belief. I need to find out ASAP, but I won't have the money for another 2-3 weeks when I get my first paycheck from my new job to visit the doctor and find out with a blood test, and I definitely cannot wait that long, I smoke cigarettes a lot and take prescriptions that could harm the baby if I am pregnant, please help. The wait is what's really killing me. I just want to know if I'm preggers or if my period is coming up soon.