Love can get complicated especially when it comes to sexual compatibility, which can bring up uncomfortable conversations. But if you do it with tact, you'll be fine.

"You have to develop the vocabulary to talk about sensitive issues," says Arlene Goldman, Ph.D., a sex therapist based in Philadelphia. "It will help you please your partner."

A recent study published in the Journal of Couple & Relationship Therapy found that communication is the most critical factor in a couple's success—it's more significant than the sex itself.

So before you say something that might cause a huge argument, here are what some experts advise you avoid when you're sexing your girl up in the bedroom:

“Did you just fake an orgasm? I'm pretty sure you did.”
Don't accuse her, says Eli Finkel, Ph.D., a professor of social psychology at Northwestern University. Instead, save your thoughts and talk about it away from the bedroom (or wherever you're having sex). When the topic comes up naturally, say, "You don't ever need to fake orgasms with me. I want our relationship to be totally honest." You'll foster mutual respect—in and out of the bedroom.

“Nope, not happening. I just want to watch TV.”
Everybody is allowed to be tired, but make sure she knows you're surprised too. Instead of just blowing her off, try saying, "I can't believe I'm saying this, but I'm too exhausted," says Finkel. Then ask for a rain check—say, for the morning, or the next night—and tell her you'll do anything she wants. "Reassuring her is important," Goldman says. If she knows you're still interested, she'll let you off easy.

“There's something really weird I want to try with you.”
"If you say, 'I know this is weird, but. . .' your partner is bound to feel conflicted," Goldman says. A smarter way in: "I'm curious about bondage. What do you think?" Starting a conversation instead of forcing her to say yes or no on the spot gives her time to think. She'll see that you view the act as a way to connect, instead of control.

“I'll probably enjoy the sex better after you take an STD test.”
What she's hearing is that you suspect she has an STD, which is a turn-off. Instead, tell her you think it'd be a good idea if you both got tested - if you're going to ask her to prove she's clean, you'd better have a golden record too.

“Is that supposed to feel good? Cos I don't like it.”
Maybe she doesn't know what you like, so show her that you're eager to improve too, says Goldman. Ask "What do you want more of or less of in bed?" You'll learn what rocks her socks, and when it's your turn to share, she'll pay attention.