It's usually quite easy to see if a boy is feeling uncomfortable with something... and if your relationship is good then they should have no trouble saying "no" to you.

I disagree with the last part of your statement. If the boy loves you and especially if you fill a real need in his life, he may indeed find it very hard to say no. He would want to please you in any way he can. So if he picks up on how much you want sex, he may consent or even initiate it, just to please you.

Regarding the first part of your statement, just because a boy may not be uncomfortable with certain actions at the time doesn't mean he may not truly regret them later. There may be a valid argument about the later regret having more to do with society's taboos than the actual actions. This may or may not be true. But regreting past actions, regardless of the reasons for that regret, can be harmful to the boy in later life.

Dakota