Oh, meow. I echo the others - these feelings are so normal and natural. For lots of women, pregnancy just isn't fun. The only thing you are supposed to do is take care of yourself. And I don't say that for your baby, I say that for you. Self care is one of the most important things you can do right now.
At 13 weeks you are also at, what I at least would consider, one of the crappiest times in your pregnancy. Pain happens as your body is adjusting to make room for your growing uterus - it might go away in a few weeks or get easier to manage. For me it subsided significantly by week 16/17. The food aversions, nausea, and exhaustion were the worst for me around that time. I remember saying over and over again, " I just want to feel like me again. I just want one normal day." Eventually I got there, or at least, pretty close, but it took a while, probably not until at least week 14/15 to have just one good half-day.
If there's one thing I don't think we women have done very well over time as we become mothers, it's this. There is so much pressure on us from the media and well-intentioned others to feel elated about being pregnant. To glow. To welcome every change in our bodies and lives as a gift. When really what we need is honesty, that it's not all sunshine and rainbows, and that's OK. A couple days after I found out I am pregnant, I had to take a long drive solo for a business trip, and I found myself perusing pregnancy audiobooks to keep me company. I came across Belly Laughs by Jenny McCarthy - written about her very un-fun pregnancy and birth, and before she got political. It was about three hours long, the exact length of my trip, and I laughed my a$$ off. If humor helps you, you might enjoy it, too.
About other people - I learned pretty quickly that there is one socially acceptable answer to the "how are you feeling" question. Many people don't want your honesty and may make you feel guilty for not perpetuating the myth that you have to feel fantastic and grateful all the time. You can protect yourself from them by coming up with some rehearsed lines "I have my good days and bad days", or something like that that works for you. And please, forgive the all caps, but OF COURSE YOU HATE UNSOLICITED ADVICE - it is insensitive and uncomfortable and rude and UGH! I could go on and on here. The bad news is that it doesn't stop. What I have learned is that trying to make it stop only makes it harder on ME, as I start to feel like I'm at war, defending myself and my new family. The good news is that... Well, OK, there is no good news but there are things you can do to make it a little easier to take. Again this goes back to self care. 1) you can try to remember that unsolicited advice is almost always about the adviser needing validation for their own decision, and not actually about you. This might cause you to feel a little sorry for them, which isn't as taxing on your emotions as being angry with them. 2) you can try to create some clever visualizations, like you are coated in something slippery or bouncy, and every time someone gives you unsolicited advice you can picture it falling off of you or just not sticking no matter how hard they try. 3) you can vent about it here with lots of women who get it, and 4) you can again develop rehearsed responses that work for you, such as "we're keeping that private". This one I have found myself practicing a lot lately - just found out we're having a boy and within 24 hours of announcing it on Facebook a friend called to share her views on circumcision. It was completely unsolicited and judgmental and blindsiding. Whether I agree with her or not, my kid's penis is none of her business, period. "We're keeping that decision private."
Lastly, yes, I do agree with the others that some if this did start to feel easier to me once I could feel and see the baby. But that was a slow change, and I'm kind of in the middle of it now. I'm finally able to feel him move daily, not big bursts of movement but little wiggles occasionally. I picture him waving Hi, like we are introducing ourselves to one another. The ultrasounds helped a little, but also were a tad awkward, getting this picture of someone who I don't recognize, and don't know yet. Sometimes it helps me to think of it from his perspective, like, he doesn't know anyone in the world yet, and we're kind of in this together. I start to feel like maybe we're both scared and confused but at least we're on this journey together and we'll figure it out. But again, those feelings are very recent and didn't come until I knew he was probably healthy, I had seen him a couple times in an ultrasound, I could feeling him moving, and I had a name and/or pronoun to associate with him.
So, to circle back on your question, what are you supposed to do? I say, have a good cry or scream, and then go do something nice for yourself. Get a pedicure, splurge on a book or gadget you've been wanting, something fun just for you. Big hugs.