I'm 6 months into my PhD

I've completely run out of motivation - really simple experiments keep going wrong and I'm finding it increasingly hard to care. Everything's starting to feel like I'm just walking on a treadmill all day and not going anywhere, I'm starting to worry that I'm just not cut out for it, having spent the last 6 years in science and the last 3 trying to get a phd.
Is this just a 6 month itch? Did you guys have it and get through it or have I got a real problem here?