Advice on ovulation...

So last month I had two positive tests and two negatives, then I had a 4 day 'period'... All month I've had thick white cm, some time watery... I just had two days of ewcm, now it's back to watery/ thick white cm.. Period isn't 'due' until 26th... Could I be pregnant and it not show yet on a test? And/or conceived last month but still had a period? Advice please? 
Anyone?????