Now, its been a month and a day and i have not had my periods.Is it possible that i am pregnant ?

Dear doctor, I have regular 28 day cycle periods. I had my last period on 27th July. Then on 6th August, My boyfriend had touched his penis by his hand and then he touched the outside of my vagina. There was no penetration of his hand. We did not have sex. He says there was no semen on his hand, but i am scared. Now, its 26th August today and i have not had my periods.Is it possible that i am pregnant ? I felt dizzy and nauseatic and bloated on 24th July, but i guess i was due to in digestion and gas. I was ok by the next day. But i m not sure if i can dismiss this as a sign of not being pregnant. I have had no other symptoms of pregnancy. Please help me as i am really distressed. Also , if i have regular periods within 1-2 days from today, does it guarantee that i am not pregnant ?