Hi hun. Pleae, please never show your jealousy in front of the child, but apart from that, it sounds like your bf is the best thing that's happened to you, so you don't want to lose his affections. Perhaps that's why it manifests itself as jealousy.
Your bf's daughter needs as much time and attention from her father as possible, and then, when she's not there, I hope those affections are transferred to yourself.
if you need a cuddle now and again - tell him, but I wouldn't go as far as to say you're jealous of the girl. Perhaps you're just seeing something in the situation that you wished YOU'D had a child? If you can look on her as the innocent party in all this, I'm sure you have a big enough heart to accept that she'll need her dad as much as you do. I'm sure you'd be horrified if someone felt like this over your son.
As for becoming obsessed about knowing what your bf's doing, where he is and so on, again, it has to do with lack of trust and/or insecurity. Perhaps when you're alone together, you can tell him that you have a problem which you want to discuss with him? Sounds as if you could do with a break as well - to get out a bit more yourself, and preferably with your partner. Also, if you have something to occupy your mind, even if it's only to have friends round for a laugh, i think you'll find yourself relaxing a bit, and not forever thinking the worst. On the other hand, if you have reason to doubt your bf, then this needs to be discussed openly. If you keep things buried, they magnify. Best of luck to you. x