Cd 20 and feeling weird (nausea?) and tired

Brooke
I have been irregular the past few months and have had dark lines on the opk but not quite as dark as the test line (so it's negative). I was averaging a 31 day cycle before the irregularity. Today I feel weird, almost like nausea or I cant tell if I'm hungry or thirsty and I'm really tired. Is it too early to be a sign of pregnancy? Any thoughts?