Am I ready for this?

For those of you who know me, do you think I am a kind, giving, caring person? Personally, I know I am.. to a point. I want to be a good person, and maybe just by wanting to be good, I am good. I try to do good things too. Never mind my slight prejudices, I don't do things to deliberately hurt people and when I have negative thoughts I generally feel bad about them... So I'm good, right? Well, lately I don't feel like a good person... Here's why: I've been taking care of my grandfather. He's always been there for me growing up, and so continuing his helping me he has let us live with him so we can save up a down payment on a house. He recently had rotator cuff surgery and is having a hard time getting around and other stuff we usually take for granted. The first night home (day of surgery) he had a hard time getting comfortable in bed. We tried for an hour to get him comfy, and finally settled on him sitting in a chair to sleep. Well, I was tired as I'm sure he was as well .. but no one got much sleep that night. The next day and night were filled with getting up from the chair, going to the bathroom, settling in the chair again (which now has more steps to it than prepping for surgery) eating meals, taking pills, refilling water, adjusting the sling for the zillionth time even tho he's not SUPPOSED to loosen it for another 3 days... by night time I was pretty tired. Then at 4:30am I am jarred awake by my grandfather shouting my name from the hallway. How the hell he got up is beyond both of us, but he couldn't get through on my cell phone (our communication system when I'm not in the same room as him.. he simply calls me and he doesn't have to shout) I don't know what was wrong with my phone but call forwarding was set.. anyway we now have a house phone in our room.. I didn't get any sleep after that, for fear that grandpa would need me and couldn't reach me. So onto Thursday.. more of the same, tho grandpa is slowly getting more of his strength back he still calls me every half hour or so to do something.. it started to wear on my nerves. I get a few hours to get out and buy my summer school books and suddenly I don't want to go back home! By this time I am so exhausted from getting up in the middle of the night and really early in the morning that I am falling asleep at the wheel. Of course, I can't leave my husband alone with my grandfather all day! How selfish would that be?!? SO I go home, and spend yet another night helping grandpa try to get comfortable in bed, only to move him back to the chair again so that he can actually sleep. Up and down until 1am, then a few hours rest.. a phone call.. I almost broke so hubby was kind enough to help grandpa to the bathroom this time.. I know this all seems like nothing. But I'm getting frustrated. And grandpa is so particular, he has to have everything JUST RIGHT. I'm trying to keep calm and not snip or argue because he doesn't need that. So because I am feeling so frustrated, I've begun to wonder if I'm really all that good of a person. I'm not a very patient caretaker. And now I've been wondering.. if I can't even handle this, how the HELL am I going to handle a baby?? Babies can't tell you what's wrong so that you can fix it. They cry all hours of the night, and I will probably get even less sleep than I have the past week. I'm exhausted now, what will having a baby do to me??  And will I be able to handle another living being being totally dependent on me, when I'm starting to break having someone only mostly dependent on me??? Is this just God's idea of practice or is it his way of showing me I'm not fit to be a mother?? I wish I knew...