I can say I was low fat and under eating plus bulimic and an over exerciser before discovering low carb/paleo-ish and back than my periods were like 4-5 months apart if they came. I think I regulated around 21 years old after discovering low carb- Atkins where I was still a binge eater that would purge only after binges (1-2 x week) but would eat low carb most the time. I got pregnant immediately with my ex while doing a semi raw paleo/ low carb thing for a month. I never used contraception before and he did ejaculate in me when we were having sex but never had I gotten pregnant before with past ex's on the occasional slip ups. I think I got pregnant within 4 weeks, however it was our choice not to keep the child.
With my husband we had sex for over a year (time we've been married) without contraception but he used the pull out method always per my request. This past May he wanted to have a baby so I gave him the go ahead a few times but I was hesitant and undecided about the matter so it was infrequent but I must have become pregnant mid June judging by my due date. I was 24, now 25. I was maybe 80% paleo, no longer bulimic for over a year, occasional oatmeal after a workout or such. When we went to Miami in May I'm a sucker for Jamaican food so along with my fatty amazing oxtail and curry goat binges I'd eat "rice and peas" (rice and beans). And than I'd have cheats like ice cream or chocolate and I did eat dairy but I was relatively good about my diet and I've always worked out cross fit style with heavy weights and minimal cardio.. I'm now 39 weeks pregnant lifted till 2 weeks ago, its been an easy (physically however not all around due to husband and I separating) pregnancy and anxious to see my semi paleo baby :) Good luck to you!!