Hi Aao9 and welcome to the Mattress Underground 
First, congratulations on your baby! Sorry to hear that you are now finding your ādream mattressā is no longer holding upā¦not entirely surprising as the body changes so drastically during pregnancy for some people!
The good thing is you have a good alternative in your guest room, which takes some part of the guesswork out of adapting your own mattress to be more suitable for you.
As you may know, any mattress you both find ideal will be based on your Stats (height, BMI, sleeping position(s) and any underlying health conditions) - thanks for providing those! - and your PPP (Posture & alignment, Pressure relief, and Personal preferences). As you are both higher BMI sleepers - but as you donāt mention your husband having any issues with your mattress, you can concentrate on your own specific comfort and support needs.
It sounds like the wool ticking and 2" 19 ILD Talalay is allowing you to ābottom outā on the firmer 28 ILD Dunlop Layer below, whereas on the Leesa, the medium firm SOL topper, even with the 1.5" down topper, is providing better support for your changing body. Keep in mind, also that Talalay Latex rubber has a different āfeelā to Dunlop; Talalay is considered ābouncierā (usual comparison is between angel food cake and pound cake).
Unfortunately, like many ābed in a boxā brands, the Leesa Original has almost no provided specifications , their website provides only:
10"
Breathable cover
Comfort layer
Memory foam recovery layer
Stabilization layer
ā¦without any listed densities, or what type of foams, or even layer heights, itās difficult to assess this mattress for suitability or support, or to get any firm idea of what the Leesa is providing that your latex mattress is not. Is it the same mattress size as your Latex mattress? Have you tried the SOL topper on your latex mattress? Or removing the plush top comfort layer with the SOL topper? As itās Dunlop, it will be more supportive. And as the Lessa was in the guest bedroom, it likely has seen less use and is probably in good shape with no divots or valleys.Even without the pregnancy, you would need more durable materials, thicker firmer layers which are recommended for High BMI sleepers. You can take a look at the Mattress Durability Guidelines to see how durable specific materials are over time. As @Phoenix says," Thickness and softness work together and because thicker layers (or mattresses) can have a greater range of compression and are more āadaptableā ā¦ itās also possible to use firmer top layers in a thicker mattress and still have good pressure relief because of the greater range of compression of the thicker mattress which can create a mattress with a firmer āsurface feelā but that still provides good pressure relief and adapts well to the body contours."
Itās not uncommon with DIY builds to need a little adjustment as your body changes - and pregnancy definitely qualifies! If you can, try to test out a few combinations - like the SOL topper on your existing bed, then as a replacement for your top latex layer,
such as:
SOL topper
2"/19ILD talalay latex
2"/28ILD Dunlop latex
3"/38ILD Dunlop latex
3"/38ILD Dunlop latex
Then try removing the Talalay layer; move up the firmer layer,
etc. it is an interesting point that you find the switched medium layer and firm so you now have med firm SOL, firm Dunlop, then medium Dunlopā¦is the plush Talalay layer still on the bed?
It can take a bit of trial and error to dial in on the best possible match for you, (as it likely happened when you got your āperfect comboā 3 years ago). This is clearly not a princess & the pea situation ā you definitely need to experiment with the layers that you already have from your combo and possibly the āfloatingā 2" latex from the guest bedroom. Hopefully youāll find just the right combination that is similar to your guest bedroom set up, which is 12" with the topper which is better for higher weights, but might not be the right long-term solution.
I also agree with @BillyIdol that the v-zone could be a potential solution, it given the circumstances, as things will likely change once youāve given birth, you should hold off on zoning for the momentā¦please keep us updated!
~ Basilio