I have a ds, he is my third child. He is five weeks old. Atm I feed him whenever and he sleeps whenever he wants. Evenings are mostly spent with him on mine or dh's lap while I'm MNetting or watching TV or even sitting outside. Ds comes to bed with me when I go to bed.
I did the same with my two dd's. Over time things started to evolve into some sort of a routine, gradually we moved to a proper "bedtime" etc., and now they are five and three and very, very good at going to bed, and have been for a long, long time.
It really saddens me when I read all these worried posts about how to get a baby of a few weeks to settle in the evening etc., and all it seems to lead to often (not always, granted) is stress and worry and more stress.
I just want to reassure you all that no bad habits will be formed if you just with the flow for now and enjoy your baby and let him/her be with you.