If you had periods on time and in the same amount and duration like before, its unlikely that you are pregnant.
If you still want to be sure you can do a repeat urine test for pregnancy
IF its negative you need to visit a gynecologist for a battery of tests to rule out cause of milk discharge from nipple.
It is usually seen in hyperprolactinemia
- a condition where blood levels of Prolactin hormone are high which can be due a tumor
or side effects of some medication like antipsychotics.
So get your serum Prolactin done along with Serum TSH, LH, FSH and testosterone
to rule out any kind of hormonal
Also its important that you stop expressing milk from your nipples.