Worrying about your exact body fat percentage is kind of a fool's errand; visuals matter more than the specific number. But oldbeancam is right that you may want to Google-search "body fat pictures" to get an idea of what people who are actually 3-5% look like (hint: that's the level of leanness that a stage-ready-bodybuilder has in the final days pre-contest).
You're probably more like 10% - which is fine, BTW. Since you mention that you're not planning to compete, just worry about your strength and appearance. No doubt you have a physique that will turn most of the girls' heads at the beach.
I also have a question about this:
Not to come off like the squat-depth police, but post a video of your squat, please. Admittedly, you're a pretty tall dude and maybe your leverages just suck for deadlifting, but seeing squat numbers higher than deadlift numbers (in a raw lifter, anyway) always makes me leery of the possibility that the squats are not so deep as they might be, and while I don't just want to harp on squat depth, this seems relevant given that you express a desire to add more mass to your lower body.