Struggling to throw in randori...

Been doing Judo now for about 8 months, going once or twice a week, and have reached the dizzying heights of 5th Kyu. The thing is, I really struggle during ranodi, and don't feel like I've pulled off a legitimate throw on anyone that I've sparred with. I've caught a couple of white belts with a very poorly executed tomonage, but these felt more like flukes than anything else, and never managed to throw anyone of equal grade before. I always seem to manage to get a grip, then have a complete blank as to what throw I can do from that position, giving my partner time to throw me or get a better grip and dominate me. Admittedly, where I train, everyone is either a higher grade than me and/or weigh more than me, but these just feel like excuses I try to use to justify it to myself.

How long should it realistically take for someone doing Judo to start being able to pull off even the occasional throw in randori? Am I being harsh on myself, or am I genuinely learning a little bit slower than the norm (I don't mind if that's the case, just would like to know...)