Hello fellow career changer! I'm in IT myself, planning on applying to a PT program this summer. I've been a consultant in the field for about 7 years.
Since my degree is in IT, I did not have any of the usual PT prerequisite courses under my belt (bio, chem, etc.). I started my journey towards completing them exactly one year ago. I have been taking them at my local community college, thankfully all have been available online. If it weren't for that, it would probably take me 2-3 times as long to do all this, and possibly a break from working.
The first part of your journey is going to be researching any PT programs of interest. Pretty much everyone on these forums is in agreement that you should always pick the cheapest accredited programs you can get into. In the end, employers don't really care where you went to school as long as you are licensed. Also consider the debt-to-income ratio as a PT (there are several threads about this). Secondly, you should look at schools that have a high passing rate for the boards, as that is a good indicator of how well they prepare you. Third, if you have a family and/or don't want to relocate, look for PT schools closest to your area. Lastly, most programs have pretty similar prerequisites but with a few differences (for example, one program might require that you take statistics while another requires medical terminology instead). Figuring out what you need to take will help you figure out a plan/timeline for completing your courses, and therefore, when you can apply.
You might have to re-take the math or science courses that you previously took; most schools require that you've completed them within the past 7 years, but I'd just double check wherever you end up applying. Perhaps some programs might be more lenient about that requirement. You won't need to complete another degree; PT schools generally don't care what your bachelors was in, even if totally unrelated. Some even prefer more diversity in their student bodies.
Other things that you will need to do - prepare for the GRE exam and begin volunteering/observing at local PT clinics. Observing is valuable in that it will help you make up your mind about whether PT is the right field for you. You will also meet therapists that can write you letters of recommendation. Again, different schools have different requirements about number of hours and such, so just do your research.
The biggest factors in a strong application are 1) your GPAs (different schools calculate or emphasize these differently; for example, some may focus on cumulative while others may only care about your prereq GPA), 2) your GRE score (some schools may not require that you take it), 3) observation hours in various settings, 4) letters of recommendation, and 5) your personal statement (as a career changer, this might be especially valuable).
As a soon-to-be applicant myself, my biggest fear has been not getting accepted anywhere due to my atrocious undergrad GPA. With that said, my main deciding factor in selecting a school has been to pick the one where I have the best chance of acceptance. Unfortunately, the program I am applying to is quite expensive but it is part-time which will allow me to work and pay off loans while attending school. It has been tough getting to this point (I'm not even fully there yet) but I'm really excited to make this change. I'm sure you feel the same way, and it is definitely doable!
Anyway, I'm happy to answer any other questions you have. Feel free to message me if you'd like. Best of luck!