Hoping you guys may have some suggestions...

DS is nearly 5 months old, I had a great birth, BF is going brillinatly. But I am so so exhausted. DS sleeps quite well sometimes, but at the moment is waking a lot at night for feeds, think he may be ready for some rice cereal. He has just got his first tooth also.
I have been eating a lot, I don't think I've put much weight on really. Still have post PG belly etc. I get to the point where my vision is blurred, sometimes double, and I have to focus really hard to not pass out. I have a history of low blood pressure, but the last time I fainted was when I was 10 weeks PG. When I feel as though I have low blood sugar I'll have juice etc sometimes this fixes it othertimes it doesn't. I haven't felt like this prior to PG with DS. Is it just from BF? I am really struggling with low energy today, feel as though I could sleep for days...

Can anyone offer some ideas? Is this common for women post birth etc?
Thank you rach x