The easy choice is to retake and apply if you get more than 21
but, I wouldn't apply now you should retake in summer, focus on your grade now and in the fall semester, and then apply when both your gpa and dat are better, and I keep telling people the same thing, what's the rush. Gap year is not the end of the world, but if you apply now, you lose money(2000-3000 dollar) on a not a great chance to get in.
Just think about it, if you apply next cycle, your gpa is higher ( hopefully), your dat is higher(hopefully) and you will have more volunteering hours and shadowing hours.
But yeah if money is not an issue, apply by all means, you might get in.
And now I'll be honest here, maybe you came to SDN, saw people taking the DAT while during their ongoing semester, and you thought it's a good idea.
yeah, sure it might be a good idea for people who have 3.8+ GPA, they are already doing well in school, so even if they focus on the dat and neglected their GPA for a part of their semester, their gpa won't be hardly affected and they can pull a better dat, but for you, your gpa was already struggling, who encouraged you to take the DAT now?
So, yeah for everyone who wants to take the DAT during spring or fall semester, think again, it is always better to take it in summer.
In most cases, you can't do well in both of your courses and your DAT at the same time, one score has to struggle or maybe both will end up bad.
Take your time, and even if people say 2 months are more than enough for the DAT, don't follow their rules, apply your own rules and don't take the test until you are entirely ready.