Thanks for the query.
As you underwent tubectomy there is less chance for pregnancy
. But very rarely tubectomy failure may occur.
Yes, hpt can detect pregnancy even after tubectomy, as it detects raised beta hcg
So you better go for urine pregnancy test.
If test comes negative, you consult gynecologist once and get examined to find out the possible cause for your menstrual abnormality and take treatment accordingly.