Is there anything wrong with having only one child?

Hi, im 24 almost 25 and my husband and I have a son who is turning 3 in march 2010. I am starting my nursing study this year and have decided to give up on trying for a second baby. I found it extremely hard having my son, not because i didnt love him but all the obsticles that go with pregnancy and generally having a newborn. he was very hard work, i was 62 kg when i got pregnant and ended with a 9p3 very long baby boy who had to be cut out due to being breach so my body took a hell time witch i am still struggling with as i never had a body problem b4. Im just not sure im strong enough to cope with the depression agin and the no sleep and the 9 weeks of painfull feeding. I feel so guilty that i may be depriving my son of a sibling but at the same time my mum has twins of 6 and the youngest boy is 4 so they are all very close, but is this enough for my son? i really want to do nursing and i do regret that i may miss out on actually enjoying a pregnancy as i found the first so hard but i havent been 100% possitive that i want another just because its soooo much work! i have one of those stubborn little men who didnt sleep and still have broken sleep and who HAS to do EVERYTHING himself lol so its only really been the last year that i have really started to enjoy him. Its nice to see other mums on here talking about just having one cause im terrified he will be left alone but we can never really know that that will happen. Is there a way to come to terms with this? i just dont think im fit to be the MOTHERLY type, i love my son very much and wouldnt change having him but the stress has bought out th worst in me and i feel if i do have another one i may lose it. Also im married to a chef and we took over a restaurant in april 09 so life is pretty busy. Have been trying for number 2 for longer then a year.