Thoughts?

Had sex on January 30th, prime ovulation time, best chance at getting pregnant. Had sex again February 13th. Got a some-what "lighter" period on February 15th. Starting morning of March 5th, all week, have been experiencing nausea with no actual vomiting. Been experiencing headaches, abdominal cramping/discomfort, beginning of the week was very gasy- but a fart was never satisfying my gasy feeling. Been tired and having a hard time sleeping. I love cheese, had a cheese wrap for a quick lunch and it tasted so bland. Few days later ate shredded cheese directly from the bag - again. love, love, love- and nothing, bland and was unsatisfying. Havent really been all that hungry, except for early morning. Lower back tenderness and warmth. Breasts feel a bit firmer, but are not sore. Sneezed about 4 times this morning, which is abnormal for me. Stuffy, running nose, but I have allergies. Next period is not expected until the 19th of March. Took a test this morning and got a bfn. but still experiencing cramping, backache, fatigue, on my way to work I got a hot flash then felt very nauseous, which lessened but continued later in the day. thoughts?? I experience cramping a day before or the day I get my period, but this has been all week!! Baby dust??