It's probably nothing, but I'll just check in case it's a symptom of something or other...
I'm 24 weeks, and keep having weird dizzy spells where I suddenly go all hot and dizzy and feel sick. Sometimes I can tell it's coming because my ears start feeling blocked up and my heart starts beating faster. Also my bump aches, like I've strained a muscle, but it doesn't feel like the braxton hicks I had with my first baby, unless they feel different with subsequent pregnancies?
Is there anything I can do? I'm getting loads of sleep and eating pretty much constantly.
I would go see the midwife and get that checked out if I were you. It's probably nothing but cardiac problems often present during pregnancy (mine did - thought I was cured of a VSD I had in childhood but up it popped giving me similar symptoms). So it's worth letting your midwife know. They may want to send you for an ECG just to check you are fine.
Of course lots of perfectly mild things can cause this, like dehydration, a cold, inner ear infection, too much caffeine etc.
Try not to worry but give your midwife a call on Monday.
I have low blood pressure and feel like that when it drops (which is often after I've eaten, as apparently the blood is being diverted from my head to my stomach), so it could be that. Not that that's much help, I went to my GP about it, and she just sent me away telling me to lie down if I feel faint (yeah, cheers for that).