We went to the zoo over the weekend since my niece/nephew were visiting and there was a petting zoo are with farm animals. I saw this HUGE sheep and asked the volunteer if it was pregnant. She laughed, said nope, and then said that it was a male sheep.
Can't even sex a sheep... still going to vet school.
If it was a wether in fleece, I can hardly blame you. There isn't so much to be able to differentiate between a ewe and wether if you can't see under the tail and there's nothing visible on the underline or crutch area.
Rams should be very easy to spot by smell and their masculine features, whether wooly or shorn, including their facial appearance, voice, and hopefully, if he's good a fertile, a large scrotum. Asuming he's not a little lamb.
Most "huge" sheep aren't pregnant. There is a somewhat distinct appearance that takes a fair degree of exposure to sheep to be able to recognize. The best thing to do is check out mammary development. For most sheep a few weeks before birth, the udder starts enlarging and should appear "soft", filling with colostrum, and progressively visible. Close to birth, it usually feels quite warm. Not all sheep exhibit enough udder development pre-parturition, though.
The rumen when quite full will make a sheep appear huge. If it's not bloated, gut fill really is a desirable thing, indicating excellent rumen capacity and good consumption of forages (grain should never look like that!!!). It will look different when they are pregnant. Besides, the lambs in utero will take up so much space that rumen capacity is severely limited, hence the need for really prime feed/forages to support the rapidly growing fetal load. My Finns look like blimps when they are pregnant!
In fact, I have a couple of aseasonal lambers due in a few weeks so this topic has been on my mind considerably.
If a ewe truly looks that big and you believe she's pregnant, take her off feed for awhile and palpate (ballot) her abdomen and see if you can bounce lambs in there. Usually if she's big and has an empty belly, the lambs are developed enough to be easily felt.
This is a really fun thing to do, and kind of impressive because few US sheep farmers know how to do it.
Anyways, don't feel bad, please. There's a procedure done on ewes close to lambing called crutching or crotching, where basically the wool around the vulva, tail, udder, and sometimes the belly is shorn, so that changes can be observed better as well as creating a cleaner birth environment. Others will shear sheep before lambing for the same reason. It took me a couple of years before I could be pretty confident in declaring a ewe in lamb, as a flockmaster.