If you're 4 weeks pregnant....would a HPT come out positive every time?

OK Women here's one for you....I was inseminated Oct. 20th. I took a 2 week test and it came out negative. I took two 4 week tests and they came out negative too. But I am 12 days late for my period and I have some (pardon the graphics) cramps, gas, constipation, lower back pain, headaches and having to pee more and all of these "symptoms" are for me slightly more often than normal. Is there any chance that I could be pregnant? Or am I just fooling myself? I kno all the excitement of me TTC could be making my period go off kilter but it was regular the last 2 months when I was worried about it then too......help anyone? Any info, tips or anything would be greatfully appriciated.