Time to go back to work I think?

Is there anyone else out there who felt more than happy to go back to work after a baby? My little boy is nearly 5 months and my maternity leave is up at the at the end of October and I can't help but feel excited to get to go back, but this is also making me feel miserable and like a selfish mother because I feel that I shouldn't be happy to be leaving him behind.

I had him in May and had so much going on with the summer and we were always busy and doing things but now it seems like everything has gone to a halt now that family and friends are back in the winter rouine of work/college etc. I just feel very bored. I spend all the day with him and we play and go for walks or a spin in the car so why do I feel so happy to leave it all and go back to work?