no, you can't get get pregnant 3 months after you are pregnant.
You can have a twin after you are pregnant. I have a set of g/g twins that were a late division. Once you are pregnant, you can have the egg split when the cells are div. When you have a late division, you get one twin that is "older" than the other one. The split is not "normal" but not unheard of (another form of very late division results in "conjoined twins" which we did not have). One twin was and still is larger than the other twin (they act like they are about a month different with their physical features (our little baby had no hair and no eyebrows while the bigger baby had a head full of hair and eyebrows...little baby had probs keeping warm and needed moniters and an isolette while bigger baby could see me while I was in my hospital room). I have ultrasound pics with one baby and then pics with 2 babies a few months later. The doctor found out about the second baby at 18 weeks when the doppler picked up an echo when checking the heart rate. Baby "b" was no place to be seen at week 8 ultrasound, but baby "a" was in site with a heart rate and all...doc thought that baby "b" was too small at the 8 week mark to be seen (there, but smaller around 5 weeks). Both girls were born on the same day (if you go into labor with one you can't stop labor for other baby with very rare instances of very preterm labor and mag. sulfate).
So, to recap while I was rambling...you can get "pregnant twice" if you have a single egg that is fert and then divides into twins. You can NOT get pregnant with a baby 3 months later unless you have like 2 of every baby making organs in your body...and in that case, the baby that is 3 months younger is going to be in trouble, it will be born early! When you go into labor your whole lower body tightens up....NOT one little isolated spot where baby's making your muscles contract! Plus, if you irritate a uterus, you will stimulate a response (labor).
HTH
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