I have irregular cycle and had unprotected sex.I missed my periods for 2 days.and for 2 days I'm feeling cramping,heartburn, dizziness, headache and low energy in my body.. Does it mean I'm pregnant? When should I check for it? Please explain

You are only 2 days late? That's not late for even the most regular of women and you say you are irregular.

Wait until your period is 2 weeks, not 2 days, late and take a HPT using first morning urine.

If you wrote it correctly, you are only 2 days "late" that is not really even late, You have to be at least 2 week late, (sometimes longer) to get a proper home pregnancy test.

When you test, use first urine of the morning.
All you feel could just be period coming