i just want to know if im pregnant or not!

hello all, I took a test (first response) last Friday and it was positive but very faint then I took one 3 days ago it was negative, took another one yesterday and the line was extremely faint. the question is am i pregnant or not and has this happened to anyone before? in my previous pregnancy i did not produce enough HCG so i was always sent for blood work, to keep track of them and they managed to increase each week. maybe that’s why it is faint? if i am pregnant i would be 4w4d. my last period was March 17, 2019 and they are always regular so it’s not like it to be this late. and honestly this is stressing me out because i am not ready for baby number #3, just had my second last January!