How come I feel very unpopular

I feel lonely and sad

Thank you for your kind answers. I thought I was making a complete fool of myself.
I'll answer your questions:

@ Kyra86:
I'm sitting in an office with two other people. The company is divided into different "departments" and in my department I always work with a permanent team. Sometimes I still have points of contact with people from my department, but not at all with those from other departments.
There are cliques (cross-departmental) who take a break together and are privately connected with each other. I am never actually asked and only notice that suddenly many people walk past my office and then take a break in large groups. I've already imposed 2-3 on myself.

I've been here for three months. The people are all my age, a tad younger, but they are all very similar. But I fall out of this similarity. I think the reasons are mainly the clique behavior and probably me too, of course, who doesn't throw herself into these cliques with full force.

As I said, I'm new, there are around 20 colleagues in my department and over 100 in the whole company. The proportion of men is very high and in my department it is very special.
As I said, there is clique behavior, but not necessarily departmental behavior that now, for example, people say once a week "Hey guys, let's have lunch together."
In general, I am not unsympathetic (okay, with one exception in my office) or particularly sympathetic.

@ Carrie-Louise:
I'm already doing the breaks. So I take delicious things with me from home for lunch, read a little, and am also outside a lot, strolling around the “city”. That's nice too, I don't have to hang out with people every day, but always isn't nice either. Especially when there are company celebrations coming up and you can't really join anyone and then stand around (yes, of course it's my own fault too).

I'm sorry to hear you've been through this before. Was it only related to you with you or did the others not exchange a private word with each other?
We're quite big, but we don't have an intranet or forum. Also not a “program” for new employees. Unfortunately.

I know that I haven't been here long, but it still weighs me down. The transition from before was probably just too hard. And now there is also a company outing, everyone has already formed room groups, planning their leisure program in cliques and I already have a stomach ache just thinking about it.