Would receiving fellatio from a woman or having anal sex with one cause a guy to become gay?
Fact 1. Despite the stories you hear on forums like this one, written by guys who claim that every single woman they every laid had multiple orgasms every time he screwed them, most women either do not orgasm from vaginal intercourse, or do so infrequently.
Fact 2. Women typically take considerably longer than men to become aroused and build up to orgasm. This poses a dilemma for guys who hope to give women orgasms through vaginal intercourse only, because they often don't have the control and stamina to hold off climaxing long enough for their partner to come (and some women just can't no matter how long they can last).
Fact 3. There are some women who enjoy being digitally masturbated and fingered, or have their partner stimulate them with a vibrator to orgasm, but there are plenty who do not.
Fact 4. Most women enjoy intercourse even if they don't orgasm, and I think overall women are more inclined than men to be satisfied with a sexual encounter that ends without them having an orgasm. But women like orgasms as much as men do, and I believe that if they consistently do not orgasm, they are going to be inclined to have less interest in having sex, or inclined to have sex less frequently, than if they usually do.
The solution: cunnilingus! As I said, there are exceptions and there is an occasional woman who really doesn't care for it. There are others who have become frustrated with it because they have experienced guys who are too rough or impatient to get them anywhere. And there are others who are shy about it because they are concerned the guy will object to the way they look, smell, or taste (they can get over this if a guy is patient and obviously enthusiastic). But, on the whole ...
Fact 5. Women love to be eaten. And most can orgasm this way, although what works for one might not work for another, and sometimes it takes a while to figure out what is most effective for a particular girl. So a guy who is patient can usually bring his partner to orgasm one or more times this way without fear of ejaculating too soon.
In my experience, most women become too sensitive right after orgasm to tolerate any more oral stimulation of their clit. But most I have been with really seem to want you inside at that point, and are inclined to fuck like rattlesnakes.