First of all, what you're going through is completely normal. You're probably going to be exhausted for the remainder of the pregnancy. The good news is that you will get a lot of it back very quickly after the baby is born. The bad news is that you still won't be getting much sleep - welcome to being a mom!
Morning sickness often fades around month 4, so the heaving will probably get better by then. I got different advice with each pregnancy (3 in all). The three best were:
1) Eat what stays down - if you can eat chocolate and chicken, eat chocolate and chicken. Every person's triggers for sickness is different. There are a few things to avoid (shellfish, undercooked meat) but otherwise don't worry too much about it. Just eat what you can.
2) Eat something the instant you wake up. I used to have a lot of "dinner" type foods first thing in the morning. Sometimes yogurt worked for me, and sometimes it didn't. Protein-rich stuff (peanut butter, meat, diary) worked best on pregnancy #3, crackers worked best on pregnancy #1. Nuts worked best with pregnancy #2.
3) Establish a bedtime routine (reading, knitting, listening to music). Having a repetitive, consistent thing you do each night will help you get to sleep and stay asleep - it's the same with kids' bedtimes!
Don't panic - you're going to be OK. This is just part and parcel of being pregnant. You're building a person, after all - it's tough work.
You may want to consider checking out some pregnancy information books - your ob/gyn or midwife should have given you one at your first checkup, in fact. This is probably the last chance you'll have to do a lot of uninterrupted reading, and the next seven months will be a lot less scary if you have some idea of what's coming up.