Flowers are dropping off orchid :(

[shallot]

I got a Dendrobium on the 6th of January 2019 and a couple of days ago the flowers started dropping off, someone online said that it needed a winter break so I moved it to the window sill (where it is colder) but I think the sunlight was too birght and made one of the leaves turn yellow. Now i have moved it back to its original spot, near a west facing window (I think) on a shelf above a radiator (the temperature is around 20°) and with a make shift humidity tray.
Please someone help im new to orchids/plants!!

[Mike H]

As long as it doesn't get direct sun it should be happy there, just don't let it touch the glass, a sheer curtain would be good once summer gets here.
A picture of the whole plant and ideally plant tag would help you get better advice.
If you bought the plant on Jan 6th it could have been in bloom for weeks already so it was probably ready to loose its blooms.
A picture of the window and radiator would be helpful also.

[raybark]

There are many reasons possible for flower drop.

If the plant was in bloom when you got it, you really don't know how long, so they could have simply begun the normal senescence process.

Sudden changes in temperature and humidity can also "blast" flowers and buds.

Not all dendrobiums need a "rest", per se. Photos will help, but not guarantee a correct ID.

[shallot]

As long as it doesn't get direct sun it should be happy there, just don't let it touch the glass, a sheer curtain would be good once summer gets here.
A picture of the whole plant and ideally plant tag would help you get better advice.
If you bought the plant on Jan 6th it could have been in bloom for weeks already so it was probably ready to loose its blooms.
A picture of the window and radiator would be helpful also.

Heres a picture of the plant, it sits on a shelf above the radiator and I do have a sheer curtain up at the moment, thanks for taking the time to help!

[shallot]

[Dorsetman]

It is a D.nobile thpe hybrid. What is it potted in ? Coir is often used ( coconut husk fibre) and that holds a lot of water, and. An easily get too wet when the plant is not actually growing a new cane.Keep it on the dryish side until that happens.

[shallot]

It is a D.nobile thpe hybrid. What is it potted in ? Coir is often used ( coconut husk fibre) and that holds a lot of water, and. An easily get too wet when the plant is not actually growing a new cane.Keep it on the dryish side until that happens.

It's not in coconut husk fibre, to me it looks like normal brown soil. Should I ease back on the watering then?

[raybark]

If it is in ordinary potting soil, that could be the issue right there.

Unlike terrestrial plants, orchids do much of their respiratory gas exchange through their roots, rather than through their leaves. As Geoff said, most often, orchids are potted in a bark mix, coconut husk, sphagnum moss, and the like, which remain open and airy to allow the roots to "breathe" while remaining moist.

What is likely happening is the roots are suffocating and dying, leading to the blossom and leaf loss. I'd repot that right away.