Are you sure you're looking at LTC/USD and ETH/USD charts? There are correlations of course, but altcoins are not entirely linked to BTC. It can often even happen that people buy up altcoins when BTC prices start to fall raising ALT prices. Economics are really complex and unpredictable, but I don't think that BTC will fall in the next few months, don't worry.
What i meant is, 2 weeks ago Bitcoin fell to 3600, and with it every alt coin price went down too. Now look at today, bitcoin prices goes up and rest of the altcoin price also going up.. So i believe somehow bitcoin has relation with altcoin market.