My boyfriend was wearing 3 layers of clothes boxers shorts and jeans

This is only a very short answer and may not be satisfactory, I can expand on this later if you like.

It is unlikely you would become pregnant from this, but I cannot say it is impossible.  Unless a male is incapable of producing sperm at all, there will be some in his precum.  Very little comparatively, and even less after masturbation, but it is there and can get you pregnant.  The odds are much lower but possible.  My understanding is that sperm can survive for 3 to 5 days, some reports say longer.

I cannot say it is impossible, but you did take impressive precautions.  I strongly doubt you will get pregnant.  If it wasn't for the occasional odd incident I would want to sat no way.  I would rather say that because if would ease your mind more.  Please understand why I cannot say that, but barring some unusual circumstances, I think  you will be fine.  I honestly can't imagine you will get pregnant from this.

Let me tell you briefly about a recorded incident during the American Civil War.  Keep in mind that although there is record of this, it does not necessarily mean it is accurate. There is some controversy it and some suspect this was to hide premarital sex.  So keep that in mind.

It was reported a soldier was shot through the testicles and continuing on to hit a female further down the line.  The woman became pregnant, and after checking out her story and medical examination to determine her state of virginity, it was decided the soldier must be the father.  They reportedly got married to do the "right thing."  Strange yes, but true?