Late but BFN

Hi, Wanted to get a bit of advice or peace of mind really. So normally my cycle is generally an average of 33 days. My last period was on the 07/03/2018 and I'm now 10 days late.(So it's 43 days since my last period) I purchased a pregnancy test on Saturday, just to see. The following morning,15/04/2018, I took the test and it was showing a BFN I followed the instructions meticulously 🤔. I have been feeling so tired 😴 and nauseous, boobs feel fuller, headaches are creeping here and there, all since I missed my period. My question is have a tested too early and has anyone not found out they were pregnant until later on in the first trimester? Any advice or similiar stories are welcome x