Stitch, our Dachshund, is 5 months old. He used to be affectionate and kind, of course he might snap a little but it was during play. Now he's become aggressive. All started when he was lying with me on the couch. When I moved my leg, he growled at me and almost bit my leg, thank goodness it was under a blanket! If Stitch is on the couch, he won't let me sit there but will growl at me. I'm afraid. I know I must now exhibit my fear but sometimes these tantrums are really scary. I can't even pick him up anymore. It's been happening for less than a week. In teh street he's very shy and afraid of everyone and everything. Does it mean he tries to pour out his frustration from the walks at home?? Every time I try to punish him for something (with a firm voice, no violence!), for example for tearing my pants to pieces or peeing in a wrong place, I get the same aggressive reaction. Please help me, what can I do?
You have allowed Stitch to become the pack leader at home. He's telling YOU what you can or cannot do. If you don't take control, and counter this behaviour immediately, he will only get worse.

By not stopping him from snapping at you during playtime, you've permitted him to think that he's the boss. In effect, you've created Stitch's bad behaviour, yourself.

Start by getting yourself a water bottle or water gun. Fill it with water and set it to "stream." Keep it with you at all times, and whenever he behaves in such an aggressive manner, immediately spray him in the face while loudly and firmly saying, "NO!" If that doesn't work, then try adding just a little bit of lemon juice to the water. Most dogs really hate the taste of lemon, so it's a great deterrant for them.

Give that a shot and let us know how you make out.
But I just didn't want to be harsh with him... Even the water gun, won't it be kinda mean? I know I will have no choice apparently but I really wanted to follwo more peaceful methods... I just don't understand why he doesn't want to obey them. Even when I punish him with voice as I wrote, I feel somewhat guilty for making him feel bad...
AnonymousI just didn't want to be harsh with him
There is nothing at all "harsh" about taking control of and disciplining your dog. If he were a child instead, and he tried to bite you, would you not discpline him?

No, using a water gun is not mean. It is the gentlest form of punishment that you can use on a dog, and does absolutely no harm. I use it on all of my cats and dogs, and they each instantly behave as soon as they get a faceful of water.

AnonymousI really wanted to follwo more peaceful methods
Dogs don't understand peaceful methods, nor do they understand words. What they do understand is actions. If you watch a pack of dogs you'll see the pack leader do some of the following things to his subordinate pack followers: growl, stare down, nip or bite, hit with a paw, tackle, roll one over, shake another dog's scruff, etc. They do not use gentle or peaceful methods or words, but they always get their message across to make the other dogs behave in the manner of his choosing.

AnonymousI feel somewhat guilty for making him feel bad
Okay, now this is your biggest problem. Again we'll go back to the example of a child ... If you have a young child, and he decides that he's going to play with your sharp knives in the kitchen drawer, would you not do something to stop him? Now, what if that child decides that he doesn't want to give up the knife, and instead is going to slash you with it, just as your dog slashes at you with his teeth? Would you not take a bit more drastic measure to stop your child from hurting you?

Dogs, just like children, learn from and thrive on the following things: love, discipline, exercise and guidance. Without any of these things, your dog or child will not behave in an acceptable manner, and will become very unruly. If you do not take charge now and become the pack leader in your home, your dog's behaviour will only continue to get worse. As of right now he believes that he is the pack leader because you don't use any discipline with him. He views you as being weak and subordinate.