I had anal sex with my boyfriend and after two days my normal period cycle come and then after 14 days of first anal I again had anal sex with my same boyfriend and then my period cycle come after 18 days of my second anal sex (which is normal and one month period cycle and routine wise) but after 7 days of last menses I feel pain in my belly (stomach), the pain like menses and I also feel like vomiting to come but it does not come.
Please tell me that why such a pain happing and why situation like vomiting happing, I am so worry, is it symptom of pregnancy?

You cannot get pregnant by anal sex.

You cannot get pregnant by anal sex.

But why I feel pain in my belly (stomach), the pain like menses and I also feel like vomiting to come but it does not come?

You have the flu perhaps, but if all you had was anal sex, you can not get pregnant.

Next even if pregnant from regular sex, you would not have signs this soon anyway.

Again, some bad food you ate, perhaps a STD or a infection from anal sex.