Nobody would tell you to leave the bastard for that not even me!
Yes, you have miscommunications. It sounds as if DH is amenable to conversations around this, so I'll include you both in this bit.
Natural is correct that more clarity (or precision, if you like) will serve you better. You said "It's a much bigger job than I thought" which, really, is an observation. You may have been hoping someone would read your mind, which may have been saying "I can't face doing that now, it's a big job" or "This is going to take a long time, I will need X hours/days at least". Speech is more efficient than telepathy
so it's best to allow yourself to follow your thoughts through verbally.
If DH's exact words were "Aren't you going to do the fence?" then you weren't imagining negativity; it was negative! People only say "Aren't you ... Don't you ... " etc when the presumed answer is No. Why would he have assumed you weren't going to do it? Perhaps he meant "Have you thought about when you'll be doing the fence?" or "Are you too tired to do the fence today after all?" Again, telepathy can't be relied on and it's usually a bad idea to assume replies before you've asked the question. It gets people's backs up, understandably!
I'm hoping both you and DH will be able to take this on board. Counter-productive verbal tics like this usually come from early years. It's possible that you were surrounded by people who always state the problem without the solution, or even discourage speech so you felt you mustn't say too much (a very British thing, that, and it's bollocks). I'd bet quite a bit that DH was surrounded by folks who think they know the answer before they ask, and who adopt quite a hectoring tone as a matter of course.
It's not as hard as it looks to overcome this sort of thing. If you're both up for it, you can good-humouredly pull each other up. Just for yourself, remember to follow your fact with a conclusion: fence is quite a big job so I will need more time / a rest first / whatever. If you forget at first, just do it again with the conclusion :)
You could also answer DH's negative enquiry with "What makes you think so?" though it'll be much better if you're both improving communication together.
Going back to Natural's idea about drama - Are there any assertiveness courses near you? There usually is one. Assertiveness training will both teach you to clarify and give you a bit of practice in a small group setting.
All the best!