If you say yes because:

• There’s no point in saying no
• They won’t listen to no
• They haven’t listened to no in the past
• You’re afraid of what they will say or do if you say no
• You’re afraid of what someone else will say or do if you say no
• You don’t believe you have the right to say no
• You don’t think you matter enough to say no
• You don’t think a person “like you” gets to say no
• You think that you “owe” them a yes
• You or they think that because you’ve done something else to hurt them, you have to say yes to this
• You or they think that because they’ve been nice to you, they “deserve” a yes
• You think they’ll no longer love you if you say no
• You think they’ll hate/hurt themselves if you say no
• You think they’ll hurt someone else if you say no
• You said yes before and don’t think you can revoke it
• You have said yes to other people and think that means now you have to say yes to whoever wants you
• You are being threatened
• You believe it is your duty to say yes
• You are being offered a reward if you say yes
• You have been told you “have to” do a particular act to be a “real” ______
• You think it’s “too late” to say no
• You didn’t understand what they wanted to
• Any reason at all other than you actually want to engage in that specific act at that specific time with that specific person with full knowledge of what it is, freedom to say no without fear of consequence, and the full belief in your own agency to make your own decisions about your body

It’s not a real yes.  It’s not real consent.  And what happened to you was still a real violation and your feelings about that are also very, very real and very okay. 

ETA: To the partners - you are responsible for getting a yes.  If you get a yes, you’re responsible for having not in any way coerced it, including through any of the methods listed here, and for being reasonably certain that your partner was in a sound frame of mind and body as well as old enough and of a reasonably similar-enough power situation to offer that consent.  If you do not obtain uncoerced consent from your capable-of-consenting partner, you have committed sexual assault/rape.  That simple. 

If you obtain consent with reasonable belief that they could give it and without coercion but one of these other issues exists in your partner’s head (such as the belief that they can’t say no because they said yes to someone else, etc) and you didn’t know that, their trauma is still genuine, their consent is still invalid, their pain is still genuine, but you are innocent of having committed a wrong.  The two are not mutually exclusive, and if you devalue or deny their pain because you didn’t know about their situation, you are still a douche.