The first time I vist a shop, they all sell them in good quantity, glass and starw aswell, but now, I cant find any, so I cant build all my furnish, I have waited a month and still no sight of them in the misc section of merchants, is annoying as I need them to light dark cornes of the house, is this a bug?

go kill some goats in the Reach.

Can you get your steward to buy them?

I ask my steward "where can I buy them" but she only tells me where to go, I go there and I cant find any, Ive been killing goats but all they contain is Goat Hide and Goat Leg, I remember With my other character I could find them on their corpses, but with the new one I did in the lastest patch I cant find any

Not all goats drop horns, and you should check ALL general traders if you want to buy them. Whichever one the steward sends you to is a hint as to where to buy them, you are not going to be able to buy them all from just one shop.

Make sure to check the Khajit caravans.

Or, if you're really stuck, do as has been suggested and visit a trader. If they don't have them, reset their inventory using the classic tricks of saving, then you should find that they are available for sale. Some people consider this cheating, and some would say its called 'checking the stock room'

The store in Morthal, whiterun and falkgreath is where i been getting my goat horns.

This sounds unlucky. I haven't personally found any on dead goats - I get them from traders. Recently, however, I've found general Hearthfire items while looting in general quest locations. Be sure to check every trader you can - I recommend Solitude or Riften in particular (they've worked for me at any rate).

Actually I noticed the Falkreath trader seems to have a higher chance of having goat horns than most, since most of us would start there, it would not surprise me if they made it a bit easier to get goat horns there. They made it easier to get large and small antlers, took me ages to get them when I was working on alchemy long before DLC turned up.

I have noticed the same problem. I built the house north of Morthal and so I check Solitude and Whiterun traders and neither seem to restock the goat horns. I haven't done much looking beyond that yet but I've built the entire house and done most of the furniture other than the chandeliers and sconces and plenty of time has passed in which those traders could have easily restocked. I'm going to check out Falkreath and Riften tonight and see how that goes and possibly the Khajit Caravans. I also tried the trader in Morthal and no luck there but I think I only checked there maybe twice. I was beginning to think the game was trolling me but perhaps I just need to stop being lazy and actually go to some different cities.

I go to ALL the traders when looking for goat horns, the Khajit Caravans have basically vanished in one game though, just left their empty tents behind. The first two characters basically built the three houses one after the other very quickly, and always the traders would run out and I would be short for the third house, a lot of goats died to donate their horns to that last house.

Well I buy from Belethor in Whiterun but as was mentioned he never gets anymore.

I usually go to Windhelm and head west along the road that follows the river past Angas MIll. I usually find several goats in this area. Other than just checking all merchants just go goat hunting...its not a grand adventure but you can practice your horseback archery while your at it.

On a side note some of the lights inside dont emit light when I install them..its very annoying.

Something like every 4th goat killed will drop horns.

I think Glass, Straw and Goat Horns are on 10 day respawning schedule rather than 2. You have to stay away from a particular store for 10 days or they will never regenerate. This is similar to how Alchemist shops work. They have some stock that replenish in 2 days, but you get much bigger stock if you can stay away for 10 days.

We don't care so much about Glass and Straw because there is never shortage of them, but Goat Horns. I had some shortage problem with goat horns myself.

If you're on a PC, another ready supply is from installing the Real Wildlife of Skyrim. This mod fills the province with all kinds of different aged and sized game which you can hunt in between questing. Goats typically drop horns and other useful items like hides, alchemy/food ingredients etc

http://skyrim.nexusmods.com/mods/9778

I had this problem too - it seemed that the merchants never restock on goat horns/glass/straw.

As someone has said above, do not enter the store for 10 days and it will restock.