[SV] Lost my first 10 lbs and am now considered in the 'overweight' BMI category! + a sodium intake question

I'm 165 cm (5'5") and in 10 days I've lost 10 lbs from 86.2kg to (190lbs) to 81.5kg (180lbs).

I'd tried keto like a month ago for two week and really enjoyed it, and then went on a two week holiday and put all the weight I'd lost back on plus more! As of the 27/12/16 I jumped back on the wagon and I'm really excited with my progress so far!

My only troubles so far have been mental fatigue (I'm currently studying for medical exams so I really need to be thinking efficiently so I'm hoping that goes away!). I think my mental fatigue may be due to low sodium, and low sodium may also be the reason I need to pee so much? I've always been on the low-ish side of sodium levels when I've had blood tests before starting keto. I've been trying my best to add salt (on top of Lite-Salt that has potassium) to all of my foods. I absolutely cannot simply put it in water (even with sugar free cordial) due to the taste! Does anyone have any tips of other ways they get sodium?