Weight loss story and pregnancy exercises

Hi all! I've got a bit of a story and then some exercise questions. hoping some of you might have some professional or life experience advice on. This is me about 9 years ago:

Prior to falling pregnant I would exercise 6 times a week, usually for about 45 minutes high intensity cardio (spin class; Attack; Step or a mixed HIIT). It was nothing for my HR to average at 150-160 during that time and to peak multiple times at 180-190. For me to really become breathless I would have to sit above 175 for a couple of minutes. In addition to the cardio I would lift weights (rotate push/pull, upper lower) for about 45 minutes each day as well. I lost about 15kg in about 8 years:

and then have slowly regained some of that weight as muscle. This was me fairly recently (this mirror is a very flattering mirror, I don't actually look this trim):

AND, this is me with a very quickly growing baby bump at 14 weeks:

My questions are:

- doctor/OB has advised me not to let my HR get above 140. Given I am barely breathless at 140 and will even hit that doing bicep curls, since I've got past first trimester I'm letting myself push up to about 155. This is getting me a little breathless then I will quickly let it drop again to 140. Im then maintaining at about 140-145 quite steadily and will stop again if it rises to 150. Do you think this is safe? I feel like the doctors are being extra cautious because HR sitting at 175 seems outrageous but I truly need that high HR to increase my fitness!

- in terms of weights: I'm now doing whatever feels comfortable but have cut out any workouts on my back (so no chest press's or crunches etc.)

- are weighted squats ok?

- what about side crunches when holding a weight? Or Russian twist type moves?

Any advice, direction to particular websites would be great. Most websites seem to be targeted toward folks who haven't exercised with great intensity and therefore Its more gentle. I understand my body is going through a process and I may need to be more gentle but I am also an athlete whose body is VERY USED to high intensity training. It seems ridiculous to lose my fitness when I should be preparing for the greatest marathon of my life! (Birth!).

Thoughts? Advice? Any similar frustrated/worries stories?

(And if you're thinking: if she trains so hard why isn't she slimmer? I love food. I eat a LOT, though relatively well. So my reduced exercise is freaking me out as I am struggling

to adjust my diet. I think I'm going to gain a loooooot of weight unless I can increase my HR 😝).