Missed period 1 pos. htp & 3 neg.?

my periods are always regular. I had it last month startin on the 25th-30th. I have had unprotected for over a month now. My period hasnt came. I have been peeing more, hungry all the time, bloated, backaches, and lower stomache pains, and sometimes i just feel sick. My husband said my are getting bigger. I took a hpt sunday morning it had a very faint second line. i've taken three more that have came out neg. I'm confused.. any ideas of why i feel this way but almost all hpt were negative? please help!!!!