s528, I just read through this entire thread and you are being confusing and difficult. Yet, I will attempt to work with what you have said.
First of all, you have had a headache for a month straight. Yes, you need to see a doctor. I know you said you are not seeking medical advice, but I needed to get that out of the way. Your headache is too persistent and long-lasting to be entirely caused by vaping one liquid on one day; it looks to me like that one vape triggered an underlying condition.
That said, your juice looks terrible. I have several bottles of juice in my cabinet from many different vendors, and none look like that. As others have said, it should remix when it is shaken, and yours does not. That is not normal. I highly recommend that you not vape any liquid from that vendor again.
Think of it this way: imagine that you had a bottle of orange juice in the fridge for a while and it separated like that, so you shook it, and it the layers would not mix together. Would you still drink it? Probably not. That is how you should view your e-juice.
I must address your saying earlier that you trust your vendor as a "professional", but not so much the opinions of random people on an online board. You need to keep in mind that anyone can sell e-liquid and call themselves a vendor, that does not make them experts. Chances are many of the people you're talking to here have more expertise than your vendor. Anybody can sell snake oil and call it the cure for cancer, would you take them at their word just because they sell it?
I know you've been buying from that guy for a while, but I've seen businesses go from selling good merchandise to bad over time to save money. It sucks but that's the way it is. Flush that nasty juice and check out the liquid forums here to find a new vendor. Then go see your doctor. That is the best advice I can offer you.