I've only just put two and two together really, and I'm not sure I'm even right!
Basically, I got my BFP mid February. Didn't have regular morning sickness, instead just extreme tiredness and heart burn.
In March I had what I thought was a vomiting bug. Started being sick - violently sick like my body was trying to expel something - about 5pm. By 10pm it was over. But it was like a bug - chugging water just to have something to bring up but eventually just the bile being forced up, violent retching, burst blood vessels in my face - sorry if TMI! I was being sick every ten minutes. I'd be sick, chug water, be sick etc. I had a bad headache and it initially started with hangover type symptoms.
In April I had a similar thing - woke up one Saturday feeling wretched, headache, aching. Same violent vomiting, retching, bile, every ten minutes - and then over in about 4 hours.
Yesterday I had another attack - went to work feeling "hungover", left work about 11am with a terrible headache, sick in the train toilet (gross!), then sick every ten minutes until the midwife called us into the labour ward at about 8pm to give me an anti-vomiting injection. I've pulled back and stomach muscles and burst blood vessels in my face from the retching - but this morning, apart from feeling thirsty (have rehydration sachets) and hungry, you would not know I had been so terribly, terribly sick just 12 hours before.
It's only just now I've realised it's the same thing, once a month. Maybe stomach bugs can last only 4-5 hours, but is it coincidence I pick up a bug once a month for the last 4 months? Or could it be something like a massive surge of hormones? Midwife was fairly blase about it, baby is moving merrily around - but I'm wondering if I should expect another attack in June :(