Could I be pregnant?

I have been irregular with my period since I started having intercourse at the age of 18 (33 1/2 yrs old now). I have never been pregnant, but have invested in ALOT of pregnancy test throughout the years because of my irregular period. I have never in all my experience came across a positive reading. Last night, I took a test when I got home from work, just because I have been feeling a little weird and wasn't sure whether it was PMS symptoms or if I was pregnant and it came out positive. I got excited, happy and even called my best friend and brother. I then waited a little while longer and did another one just to be sure, but nothing was read in the test, so I went to the store and bought another pack, different brand, not the same one, because I had purchased the last one of the positive reading brand, which was a CVS brand one. I went home and took another and it said negative. I took another one this morning and it again said negative. I called and made an appointment for an ASAP walk-in today at 3:45pm. My girlfriend told me her daughter-in-law took about 8 to 10 home pregnancy tests and they were giving her both positive and negative readings because it was early in the pregnancy when she was testing and today she is 6 months pregnant. I know I won't know for sure until I see the doctor today, but was wondering if this is a normal experience with women? This has never happened to me and I can tell you I have taken over a hundred of those tests and have never got a positive reading. If I am, I am happy about it, no doubt, but it would be a bummer if I wasn't but yet got a positive reading.

Sometimes different tests have different sensitivites, so when you are very early, and your HcG is still low, it may not be picked up. Best of luck!

Thank you Jennifer. I was doing a bit more reading from yesterday and last night and it seems that the sensitivities of the test themselves makes a difference as to what stage you are in, in the pregnancy. The doctor gave me a vaginal ultrasound, but he too told me it is too early to even see anything in the uterus, but did state that there is swelling in the uterus. I was sent for blood work this morning, then again Friday morning, for my follow-up appointment with him on Monday to see what my HCG levels are reading in the bloodwork. Wish me luck!