bf pretty much forced me to send nudes?

{first of all, I'm 15, and he's 18. we met because we're both in our hs drumline, so we're together almost nonstop. the age gap can be unsettling, but -until now- he's always been respectful about how I'm a minor & how he could take advantage of that.}
      warning: this is pretty long 
      it took us 6 months just to have our first smooch... 😂 so I didn't think he'd ever be the type of person to jump on me (not literally) for sexual things. 
      anyways, fast forward 11 months into our relationship... I didn't have a snapchat because I'm reallyyyy camera-shy. he's been begging me to make one, so I did. 
      the day after I made a sc, I sent him a picture of my legs in a bubble bath. I just thought it was cute lol, but almost immediately he said "send nudes". he didn't even say please! but, whatever, that isn't even the bad part 
      I told him I was nervous. I was. I didn't say no, because he made me feel like I couldn't. I also said I was uncomfortable. 
      but then he said "the one time I actually want to exchange 😭" ???? he kept trying to make me feel guilty, like I was the bad guy...
       he said "what if I send first?", and just went ahead and sent his nudes... keep in mind, I didn't ask. I asked if I had to send some back, and he said yes. (because if I didn't, it'd be "unfair"
      I told him I didn't like feeling pressured. he said sorry, & he said he "wasn't pressuring me" ??? 🙄
       anyways, I tried to make it seem like I was enjoying the conversation... so I said something along the lines of "I wish you were here with me rn" and he said "I wish this was a fair trade lmao" 
      he kept asking when I would send some, if I'd send tomorrow, the day after, etc. so I just sent some to shut him up... 😓 and he screenshotted them!! 
      his mom checks his phone. I asked if the only reason he wanted me to make a sc was for nudes, and he said yes... (ouch) so I don't understand why he'd screenshot them?? he's even said it himself that even if he deleted pictures his mom could check the backup or something 
      
      I told him I didn't want anyone else seeing those & he said he wouldn't do that, but it still scares me.... I'm just really scared in general. I talked to him about it yesterday, & here's the screenshots: 
(our friend evie always asks questions so we call her 20 questions... that's what I meant by "20 questions like evie")
      I hate how he didn't have actual responses. I told him how I felt, but he didn't seem to be listening? so, I'm not sure it sank in. :( he also randomly asked me for my bra size yesterday. 
      is it reasonable to be worried?? am I being overdramatic? I just want opinions/advice, please... + I'm sorry this is so long lol