At 7 months, my DS was not on many new foods. We started soilds at 6 months and followed the 3-day rule, sometimes 4-5 days, plus continually offering the old foods as well, so my guess is that he probably had 8-10 foods at 7 to 7.5 months.
Bananas do tend to cause constipation if they are unripe. The browner and thinner the skins are the less constipating they are. I only tended to give him a quarter of a ripe banana every few days at the most.
If you bake your fruits, like necatrines and plums (also apples, peaches, pears, apricots...) , they are softer, sweeter and so much tastier. I cut them in half longways, pried the pit out (if I could not get it out raw then it will come out when cooked), put open side down in a baking dish in say 1-2 cm of water, and pop in the oven (never paid much attention to temp, maybe 180 - 200 degrees I guess) for 30-45 minutes, until the skins are all wrinkled. When you take them out of the oven scoop them out of the dish and let them cool on a plate (ie not in the cooking water) and when cool just slide the skins off. They don't need to be pureed then as they are just soft and mushy already. I would freeze them in portions or put a few in the fridge and mixed them in cominations, added about an inch of mushed banana to sweeten if needed, too. I still do this (my DS is nearly 3!) and add to plain yogurt to sweeten it up!
