Really late period and negative test. Please help!

So my husband and I about a year ago were actively TTC for a year, we had given up and just stopped trying. We were in the middle of moving to the UK from the states and wanted to get settled before trying again. After 5 months of being in the U.K. I got off of birth control and we decided that we were just going to go on with our daily lives and if I got pregnant we were ready. We had realised hat actively trying was very stressful and we didn't want to put all of that stress into having a baby. I have been off of birth control for 4 months now and have had regular periods ever since the day I quit. We are back visiting the states now and my period didn't show up on time, which I just put it off as stress and jetlag as both of those things are known to cause late periods. Well now I am 12 days late with no signs of my period and also no signs of being pregnant. I have taken 3 different home pregnancy tests all of them being a negative. I have never had a period be this late before and my husband keeps saying he thinks I am pregnant and getting his hopes up. If anyone has any advice to offer I would really appreciate it! I am gonna take one more home pregnancy test tomorrow morning and if it's a negative my husband wants to get a blood test. Thank you for all your help in advance! Also sorry it's so long!