FeedWordPress is the easiest plugin for this tht I have come across. But only about one-quarter adult feeds
actually verify so that might be your problem...
All that said... quote: "aggregate
my feed". You are talking about pulling in third-party feeds and not about making your feed available? I assume so since WordPress generates your feed for you.
But if you do mean your own feed, then the first step would be to
validate it.