I really screwed up during my undergrad BS and got a 2.5. I really need to raise my gpa and I was wondering whether I should retake classes and go for the SMP or go get a second BS?
Realistically, you should expect to need to to both. Because of the "A" in GPA, your 2.5 will never grow into competitive range. 4 more years at a 4.0 could get you to a 3.25, which could get you into an SMP. (I suggest that you need to get over 3.0, at a minimum, before pursuing an SMP.)
You don't
have to do a second BS, but you'll probably want to, because you need multiple years of additional undergrad. Without being enrolled in a degree program, it's more difficult to get funding, register for classes, and get access to advising etc. The alternatives to a 2nd BS are being a "nonmatriculated" or "non-degree-seeking" or "5th year" or "postbac" student.
Also, for retaking classes, can I retake them at any 4-year Uni or does it have to be at my original school?
Doesn't matter. Take classes where you will succeed. You have to get A's from here out. Don't do community college: the cases where this would be acceptable don't include sub-3.0 GPA repair.
Act. I've looked around some more and I think my main concern is what postbac programs think about repeated classes. I got a C in several chemistry classes and I heard that just repeating several courses won't be looked on favorably? but doing those courses towards getting a 2nd bs would be ok? I just need to raise my gpa to even meet the minimum for some of the programs...help~~
For MD school GPA calcs, the repeats just work like fresh coursework. From the perspective of appearing to be a strong academic candidate, you'd want to take upper division science as well. Otherwise you just prove that you need 2 tries to get a good grade. Regardless, you have to repeat any prereqs that you get less than a C in, and having lots of Cs in prereqs won't get you in, nor will you be ready to do well on the MCAT. So repeats are a given here.
I recommend looking into DO - see the pre-osteo and osteo forums.
Don't post questions until you've done lots of reading there. DO schools forgive old grades for repeated coursework, unlike MD schools, and the admissions stats are a bit lower. Plus getting residency after DO school gives you access to "MD" residencies much more so than Carib. Look for posts from TexasTriathlete, who started from a 2.6 (I think).
Either way, the 2.5 you're starting from is far and away the dominant impression reviewers will have of you. You have a HUGE burden of proof to demonstrate that you can handle the rigors of a medical education, and from here out there's no room for error. Don't worry about how the details will be perceived: work on the big ticket items, GPA and MCAT score.
Personally, with your GPA, I would do everything that I can to get into a SMP. I doubt a second BS will do you any good.
Of the SMPs that get people into med school, the lowest GPA requirement is 2.75 (and that 2.75 student would have to have an AMAZING story). From a 2.5, the OP is looking at multiple more years of undergrad.
And with multiple years of undergrad to do, it's very difficult to manage
without being a degree-seeking student. The additional degree isn't interesting: registration priority and financial aid
are interesting.