What Could Be The Cause For Missing The Periods And Had Vaginal Yeast Infection, Cold Sores On Lips, Hypothyroid And Rapid Gain Of Weight?

Hello. I am a 35 year old Canadian woman, wife and mother with 2 children, ages 8 and 3. I have never missed a period in all my life however I did not hab=ve one in December and cant recall November either to be honest. I do think that I remember in October or early November having a period and then having bleeding again for a few days and thinking ..."didn't I just have my period a few weeks ago" ?!!! I don't really keep track as I'm married." anyhow I still have not had a period. I recently had a vaginal yeast infection, severe cold sore on my lips and was vomiting several times a day for over 3 weeks, now occasionally. I have extreme fatigue,weight gain,my pants are too tight to do up, my waist line has puffed out/filled out and my breasts seems fuller and bigger. I have major urinary frequency throughout the night, several times for sure. ive been getting mild headaches and am super hungry even at night. my husband and I have been using condoms but he doesn't always withraw right away. ive lloked it up and it says that that could cause leaking and pregnancy. I am overweight and have hypothyroidism since after my last pregnancy. the thing is I took a few at home pregnancy test and they ,all 3 have said negative. I took 2 a few days apart the end of December and the last one early January. I used them in the evening not in the am. ive read up on false negatives due to urinary frequency and dilkution and also about people who are pregnant for months without knowing. im wondering if that me. I feel pregnant physically. I believe a bllod test is the only wayn to find out. sometimes I wonder is it hypothoyroidism and hormal changes due to being overweight ?