Definitely shin splints. I had them when I was doing too much running too soon. As my doctor said "your body is telling you 'I don't like this.'" I stopped for 2 weeks, did biking instead. Then started again slower and with less mileage until my body gets stronger.
Exercising more won't necessarily make you lose weight faster. Your muscles will like retain water with all that running. Just keep at your slow and steady pace, don't be in such a rush to "finish" that you hurt yourself.
It's about commitment, not motivation.