I am concerned that the doctors you may be seeing for this advice, and perhaps the one who did your "liposculpture" 3 years ago, may not be fully-trained and American Board of Plastic Surgery-certified plastic surgeons. Please understand that many doctors who claim board-certification may be certified by specialty boards that have nothing to do with plastic surgery, and a few by entirely "bogus boards." Read about this in my article on the About tab of my Profile page on this site titled: "Why Board Certification is Critical in Choosing a Plastic Surgeon."
My first concern about this was raised when you described having "liposculpture" after two pregnancies, when you should have been advised THEN that you were a better candidate for tummy tuck surgery, and that lipo (any kind) would simply further deflate your already-stretched abdominal skin. Perhaps this (liposuction) was what you asked for, but any reputable plastic surgeon would simply have told you that this was an incorrect request and given you the proper advice--saving you the unnecessary cost, risk, and healing for an operation that you now know wasn't the one you really needed. That, of course, is why you now seek the tummy tuck you should have had in the first place.
My second concern that you might not be seeing "real" plastic surgeons is your statement that they seem reluctant to perform a tummy tuck, and give you the absolutely bogus and incorrect excuse about skin being previously "separated" causing circulation problems. Any fully-trained and reputable plastic surgeon would know that (even ill-advised) liposuction 3 years ago has only INCREASED the blood flow in the now-healed abdominal skin flap (so-called "delaying the flap") and that your risk of circulation problems (ischemia) is actually less now that everything has healed. Maybe they are reluctant to do a tummy tuck because they are not "real" plastic surgeons and never learned how to do these operations! They just don't want to tell you that, because it tips their hand about not being what they imply they are--"real" ABPS-certified plastic surgeons.
I can think of only extremely rare and unusual situations (severe scarring and/or infection at the time of "liposculpture") in which I would have any concern about doing a tummy tuck in someone who had healed normally from this surgery 3 years in the past!
Something is rotten here, and it is the advice you have been receiving from those who seem to be "scaring" you! See several other ABPS-certified plastic surgeons and get some proper advice. I suspect it will be more similar to what I have just written, and not at all to what you have been told previously! Good luck!