If using concealer helps your appearance, and gives you a little confidence boost, then I say go for it.
I'm 22 witth a diffuse NW5 or so (my recession is at about NW3) and I use concealer all the time. The thing is, I've learned to not think of the concealer as anything other than what it is: another hair product. It's not a shameful secret, and it's not a magical lifeline.
If you can get the right mindset about it, it's a great tool to help with styling. You just can't let it (concealer, hats, surgeries, wigs, shaved head, whatever) rule your life. All of that stuff is just something to make you feel a bit better about yourself and give you a little more choice in how to style your hair.
As for relationships, I was open with my fiancee from the start. We were friends before we started dating, so she knew I was losing my hair and that I used a bunch of different stuff to try and thicken it up. It wasn't me trying to hide it like some horrible curse, just me using a little extra help to thicken up what nature gave me. She was cool with it, as have been most people I know.
Accepting that you're balding and shaving your head aren't the same thing. I accept that I'm a pretty bald guy for my age (or any age), but that doesn't mean I've given up or shaved my head. I like having my hair longer, so I keep it long and do what I can to make it look nice.
That being said, I also accept that I'll get to a point, probably in the near future where I'll be pretty close to slick bald, and concealer won't work for me at all (it's getting that way now). At that point, I'll have to decide to either go without concealer, get a bigger hairpiece, or cut my hair. But the important thing is to keep your options. Just because you're balding doesn't mean you have to shave it all off. If you want to, great, but if you don't, that's cool too.