Period came on for two days. skipped a day then came back on instead it was brown blood which i know is old blood. could i be pregnant? now it's off

Yes: If you're sexually active then you could be pregnant. Why not take a home pregnancy test and see? They are relatively inexpensive and quite accurate. Otherwise, pretty common for you to have some days of period with bright red blood, then even a day with no blood, followed by some brown blood. This pattern doesn't typically imply pregnancy.