Hi Bertie,
TTC and losing weight are probably two things that dont go too well together. I guess you might have to make a decision, do you want to fall preggers, or do you want to be smaller. Unless you are grossly overweight, I can't see the problem in carrying a bit extrta when TTC. (When I say a bit, I mean about 10-20kg over)
I was exercising fairly often until about 3 months, and then often until about 5 months pg playing netball. But my body was used to it, and after I fell pregnant, there were changes in my body that made me start to slow down. Specially the cramps in my tummy at 3am after 2 games of netball, and the nauseous feeling that comes along when you have done too much.
I would suggest that its probably not a great idea to be putting the body through a boot camp - regular exercise that youa re used to should be no problem for the first few months, but anything strenuous could over-tax your body.
There's no surprise that after 3 months of TTC our baby eventually "stuck" when we were on holiday in Vietnam.
At then end of the day, its your call, but maybe take it a bit easier? And I certainly wouldn't be excessively dieting if you are TTC.
Hope that helps,
Fi