Hun, I'm the same height as Bunny, and in my life I have weighed as low as 125 .. when I was anorexic ... it lasted about three months.
I also weighed 145 once ... I think that lasted around six months ...
Stuck at 165 the longest, ten or eleven years, probably won't see that again, either.
Granted, I'm a solid 5'9 and a pinch, and I'm big framed, but 5'8" and 125 lbs is actually at the lowest end of the BMI scale, verging on medically UNDERweight.
Why not drop the focus on the numbers and just try revising your body fat percentages? Build some muscle, drop some body fat? Because 145 is NOT fat for 5'8".
Really, the scale is just evil, totally, utterly, completely evil.
But otherwise, welcome darlin' and if what I said hits you wrong, screw it and forget I said it, I hope you achieve your goals no matter what