Obviously then you have to start with the definition of 'sex'. If 'sex' is just the final act whereby a man and a woman engage in the ultimate act of penetration for the sake of procreation...then sex is very narrowly defined.
People stick damn near any and everything in their orifices. They put their junk INTO damn near anything. If it is for the sake of gratification then surely it is a sexual act. But if it is only defined as the 'ultimate' sexual act between two consenting adults, male and female, for the purpose of procreation...then...there arent many people having 'sex'. If a blowjob isnt 'sex', any more than a boob job, or a handjob, or masturbation, then neither is anal sex (umm NOt sex...anal...ass pounding...): all just sexual deviations from the ultimate norm of procreative sex.
SO...what is 'sex' defined as?