I am having a problem with missed periods. I am 20 years old, sexually active with 1 current partner. We have been trying to conceive for 1 year and 6 months. I missed my period in April, had a regular period in May through July, and missed August and September. I have taken 3 hpt s and all we negative. I am experiencing bloating, gas, heartburn, and fatigue. I have an OBGYN appointment on Monday but I want to know what could be causing these symptoms and still have negative hpt tests.