2-4day periods past few mos & having pregnancy symptoms

I am 23 married with a 2 yo. I have not charted periods but the past few months they have been only about 4 days long. I am not on birth control and do not use protection when we do have sex (which is occasionally the past few mos and start but dont finish sex which is frequently). I have been having periods on different days of the month the past few periods. (Dec 9, Jan 6 or so, and havent started this month yet for Feb) If I go by the 9 then I am a day almost 2 late if I go by the 6 or 7 I am 3-4 days late this month and if I follow the pattern of my period dates being aout 3 days less each month then I am about a week late. I have been so tired I cant get out of bed, nausea, cramping, white/clear discharge, constant hunger even after eating, and FREQUENT urination, and emotional. I dont even know if I am late enough to take a test or not. I am not even sure where my cycle is messed up if I can even get pregnant! I am afraid if I am pregnant that I am a couple months along. I havent taken a test because I have had about 2-4 day light-medium flow periods that past few mos normally I have about 5 day all heavy. So do u think it is necessary to take a pregnancy test NOW or wait another week or so? And is it even possible to be pregnant with my cycle so irregular? I know with my son I was almost 2 mos pregnant and didnt even know since I then didnt chart periods and was irregular as well.

I took a test today and it was a faint negative. So light I could barely see anything. I have taken Equate brand before including getting a positive when I was pregnant with my son almost 2 yrs ago. I have taken them before since him wasnt pregnant but had a BRIGHT negative - why is it faint negative? Is there a reason.