I went on antibiotics and finished about 1 week ago.i am now 10 days late for my period and took 3 neg test. also had yeast infectio could i be preg?

Possibly: It is possible you are pregnant, but there can be other causes of the period being late such as stress, an illness, hormones being off. You didn't say whether you are also on birth control pills, but some antibiotics can make the pill less effective. Antibiotics also make you more likely to get a yeast infection. You might want to see your doctor and get a blood pregnancy test.